JP3881766B2 - Automatic vehicle steering system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automatic vehicle steering apparatus for automatically parking a vehicle without depending on a steering operation of a driver.
[0002]
[Prior art]
Such automatic steering devices for vehicles are already known from Japanese Patent Application Laid-Open Nos. 3-74256 and 4-55168. These automatic steering devices for vehicles use an actuator of a conventionally well-known electric power steering device, and control the actuator based on the relationship between the movement distance of the vehicle stored in advance and the turning angle, thereby allowing back parking and Parallel parking is performed automatically.
[0003]
[Problems to be solved by the invention]
By the way, the conventional vehicle automatic steering device automatically steers the wheels by the actuator of the electric power steering device while the driver operates the brake pedal or the accelerator pedal to control the vehicle speed. The vehicle speed during automatic steering control is not always constant. Therefore, in order for the vehicle to move along a predetermined movement locus, it is necessary to increase the driving speed of the actuator as the vehicle speed increases.
[0004]
However, if the drive speed of the actuator is increased, the steering rod hits the moving end when the turning angle of the wheel reaches the limit position, and noise is generated by the impact or the turning angle fluctuates. The movement locus of the vehicle may shift. In particular, when the steering torque detecting means stops the automatic steering control when the steering torque detecting means detects the driver's spontaneous steering operation during the automatic steering control, the steering torque detecting means detects the pseudo steering torque due to the impact, Therefore, there is a possibility that the automatic steering control is stopped.
[0005]
The present invention has been made in view of the above circumstances, and an object thereof is to prevent an impact from occurring when a turning mechanism operated by an actuator during automatic steering control reaches a limit turning state.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention provides a movement locus setting means for storing or calculating a movement locus of a vehicle to a target position, an actuator for turning wheels via a turning mechanism, and a movement locus. An automatic vehicle steering apparatus comprising actuator control means for controlling drive of an actuator based on a movement trajectory stored or calculated by a setting means, comprising detection means for detecting a turning state of the steering mechanism. , the actuator control means, wherein at detected steered state detection means executes the reduction control for reducing the driving speed of the actuator when approaching the limit turning state, the vehicle speed is less than the predetermined value at low vehicle speed The reduction control is not executed even when the steered state approaches a limit steered state, and the invention of claim 2 The movement trajectory setting means for storing or calculating both movement trajectories, the actuator for steering the wheel via the steering mechanism, and the driving of the actuator based on the movement trajectory stored or calculated by the movement trajectory setting means. An automatic vehicle steering apparatus including an actuator control unit includes a detection unit that detects a steering state of the steering mechanism, and the actuator control unit detects that the steering state detected by the detection unit When the steering speed approaches a limit steering state, the reduction control is executed to reduce the drive speed of the actuator when the steering state approaches. It is characterized by not executing . In the present invention, “the limit turning state of the steering mechanism” refers to a limit state in which the turning angle of the wheel does not increase any more even when the actuator is driven.
[0007]
According to the above configuration, when the actuator is driven to steer the wheel during automatic steering control, the actuator is driven when the steered state of the steered mechanism that transmits the driving force of the actuator approaches the limit steered state. Since the speed is reduced, it is possible to avoid an impact on the steering mechanism in the limit turning state. Thereby, generation | occurrence | production of a hitting sound can be prevented, the shift | offset | difference of the movement locus | trajectory of a vehicle can be prevented, and it becomes possible to improve the durability of an actuator and a steering mechanism.
[0008]
In particular , according to the above-described configuration of the first aspect, the actuator driving speed is reduced only when the vehicle speed is equal to or greater than a predetermined value. Sometimes, it is possible to avoid a reduction in the driving speed of the actuator insignificantly and to secure a more accurate movement trajectory. Further, when the vehicle speed is less than the predetermined value, the possibility that the impact is generated is low. Therefore, the reduction control of the actuator drive speed is not executed even when the steered state approaches the limit steered state. In addition, although the predetermined value of the said vehicle speed is set to 5 km / h in the Example, the value can be set suitably.
[0009]
In particular , according to the above-described configuration of the second aspect, when the turning speed increases to a predetermined value or more, the driving speed of the actuator is reduced. Therefore, when the turning speed is high, a large impact is likely to occur. The occurrence of impact can be effectively avoided by reducing the above. When the turning speed is less than a predetermined value, the impact is unlikely to occur. Therefore, even when the turning state approaches the limit turning state, the reduction control of the actuator driving speed is not executed.
[0010]
The invention of claim 3, in addition to the configuration of claim 1, wherein said movement locus setting means, characterized by storing or calculating the movement trajectory as the relationship of the wheel turning angle of the relative movement distance of the vehicle According to this configuration, since the movement locus of the vehicle is stored or calculated as the relationship of the wheel turning angle with respect to the movement distance of the vehicle, a constant movement locus is always obtained even if the vehicle speed fluctuates during automatic steering control. Can be secured.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on the embodiments of the present invention shown in the accompanying drawings.
[0012]
1 to 6 show an embodiment of the present invention. FIG. 1 is an overall configuration diagram of a vehicle equipped with an automatic steering device, FIG. 2 is an explanatory diagram of the operation of a back parking / left mode, and FIG. 3 is a mode selection. FIG. 4 is a diagram showing the structure of the electric power steering apparatus, FIG. 5 is a diagram showing a drive circuit for the steering actuator, and FIG. 6 is a flowchart for explaining the operation.
[0013]
As shown in FIGS. 1 and 4, the vehicle V includes a pair of front wheels Wf and Wf that are driving wheels and a pair of rear wheels Wr and Wr that are driven wheels. Steering wheel 1 and front wheels Wf, Wf rotate integrally with steering wheel 1, steering shaft 2, pinion 3 provided at the lower end of steering shaft 2, steering rod 4 having rack 4 ₁ meshing with pinion 3, The left and right tie rods 5, 5 provided at both ends of the steering rod 4 and the left and right knuckles 6, 6 connected to the tie rods 5, 5 are connected. A steering actuator 7 made of an electric motor is connected to a ball screw mechanism 8 provided on the steering rod 4 in order to assist the operation of the steering wheel 1 by the driver or to perform automatic steering for garage entry, which will be described later. The ball screw mechanism 8 constitutes a steering mechanism of the present invention.
[0014]
The steering control device 21 includes a control unit 22 and a storage unit 23. The control unit 22 includes a turning angle detection means S ₁ for detecting the turning angle θ of the front wheels Wf and Wf based on the rotation angle of the steering wheel 1, and twisting of a torsion bar interposed under the steering shaft 2. Based on the steering torque detection means S ₂ for detecting the steering torque of the steering wheel 1 based on this, the front wheel rotation angle detection means S ₃ and S ₃ for detecting the rotation angles of the left and right front wheels Wf and Wf, and the select lever 11 are selected. A shift range detecting means S ₄ for detecting a shift range (“D” range, “R” range, “N” range, “P” range, etc.) and a steered state are detected based on the left and right positions of the steering rod 4. signal from the turning state detecting means S ₅ Metropolitan is inputted. Turning state detecting means S ₅ constitute a detecting means of the present invention.
[0015]
The front wheel rotation angle detection means S ₃ and S ₃ output a pulse every time the front wheels Wf and Wf rotate by a predetermined angle, and a constant determined according to the radius of the front wheels Wf and Wf is set to the number of detected pulses. By multiplying, the moving distance X of the vehicle V can be calculated. The outputs of the pair of front wheel rotation angle detection means S ₃ and S ₃ are the high select value, the low select value, or the average value.
[0016]
Movement limit position in the left-right direction of the steering rod 4 is regulated by the operating range of the ball screw mechanism 8, said turning state detecting means S ₅ is the steering rod 4 has reached the vicinity of the movement limit position, That is, it is possible to detect that the ball screw mechanism 8 has approached the limit position of the operable range (that is, the limit turning position).
[0017]
Further, a mode selection switch S ₆ and an automatic parking start switch S ₇ operated by a driver are connected to the control unit 22. As apparent from FIG. 3, the mode selection switch S ₆ is four parking mode, i.e. reverse parking / right mode, reverse parking / left mode, select one of parallel parking / right mode and parallel parking / left mode It has four switch buttons corresponding to each mode. Automatic parking start switch S ₇ is operated to start automatic parking according to any of the mode selected by the mode selection switch S _6.
[0018]
The storage unit 23 constitutes the movement trajectory setting means of the present invention, in which the data of the four types of parking modes, that is, the relationship of the reference turning angle θref with respect to the movement distance X of the vehicle V is previously stored as a table. It is remembered.
[0019]
Thus, the control unit 22 controls the steering actuator 7 based on the signals from the detection means S _{1 to} S ₅ and the switches S ₆ and S ₇ and the parking mode data stored in the storage unit 23. The operation and the operation of the operation stage teaching device 12 including a liquid crystal monitor, a speaker, a lamp, a chime, a buzzer, and the like are controlled.
[0020]
As shown in FIG. 5, the drive circuit 31 of the steering actuator 7 includes four transistors T _{1 to} T ₄ provided between the battery 32 and the steering actuator 7, a power relay 33, and a fail safe relay 34. The When the two transistors T ₁ and T ₄ are turned on by a command from the control unit 22, a circuit indicated by a thick line in FIG. 5A is configured, and the steering actuator 7 is driven in the left turning direction, for example. When the two transistors T ₂ and T ₃ are turned on, a circuit indicated by a thick line in FIG. 5B is configured, and the steering actuator 7 is driven in the right turning direction, for example. Drive speed of the steering actuator 7, i.e. the turning speed is controlled by changing the duty of each transistor T ₁ through T _4.
[0021]
In order to generate a braking force on the steering actuator 7, two transistors T ₁ and T ₂ are turned on as shown in FIG. 5C, or two transistors T ₁ and T ₂ are turned on as shown in FIG. _3, T ₄ can be turned ON. As a result, a short circuit indicated by a thick line is formed, and braking force is generated by consuming the regenerative power generated by the steering actuator 7 with the internal resistance of the short circuit. At this time, the magnitude of the braking force can be arbitrarily controlled by changing the duty of the transistors T _{1 to} T ₄ .
[0022]
Next, the operation of the embodiment of the present invention having the above-described configuration will be described.
[0023]
During normal not used to automatically steering control (when the automatic parking start switch S ₇ is not ON), the steering control apparatus 21 functions as a general power steering control unit. Specifically, when the driver operates the steering wheel 1 to turn the vehicle V, a steering torque detecting means S ₂ detects the steering torque inputted to the steering wheel 1, the control unit 22 based on the steering torque The driving of the steering actuator 7 is controlled. As a result, the left and right front wheels Wf and Wf are steered by the driving force of the steering actuator 7, and the driver's steering operation is assisted.
[0024]
Next, the content of the automatic steering control will be described by taking the back parking / left mode (a mode in which the vehicle is parked while backing to the parking position on the left side of the vehicle V) as an example.
[0025]
First, as shown in FIG. 2A, the vehicle V is moved to the vicinity of the garage where the vehicle V is to be parked, and a predetermined reference (for example, a door) is set with the left side of the vehicle body as close as possible to the garage entrance line. The vehicle V is stopped at a position (start position (1)) where a mark or a side mirror provided inside the vehicle coincides with the center line of the garage. And turned ON, the automatic parking start switch S ₇ with to select the back parking / left mode by operating the mode selection switch S _6, the automatic steering control is started. While the automatic steering control is being performed, the operation stage teaching device 12 displays the current position of the host vehicle, the parking position, the predicted movement trajectory of the host vehicle from the start position to the parking position, the return position for switching from forward to reverse. In addition, various instructions and warnings such as operation of the select lever 11 at the turn-back position (2) are given to the driver by voice from the speaker.
[0026]
With the automatic steering control, the driver can loosen the brake pedal 9 and cause the vehicle V to creep, or the accelerator pedal 10 can be slightly depressed to drive the vehicle V without operating the steering wheel 1. the front wheels Wf, Wf are automatically steered based on the data of the selected by the selection switch S ₆ reverse parking / left mode. That is, while the vehicle V moves forward from the start position (1) to the turn-back position (2), the front wheels Wf and Wf are automatically steered to the right, while the vehicle V moves backward from the turn-back position (2) to the target position (3). The front wheels Wf, Wf are automatically steered to the left.
[0027]
As apparent from FIG. 2 (B), during automatic steering, the control unit 22 adds the back parking / left mode data read from the storage unit 23 to the front wheel rotation angle detection means S ₃ , S ₃ . The reference turning angle θref is searched by applying the moving distance X of the vehicle V calculated based on the output. And wherein calculating a deviation E (= θref-θ) based on the norm steering angle .theta.ref and the steering angle theta input from the steering angle detecting means S _1, the steering actuator so that the deviation E is zero 7 is controlled. At this time, since the data of the reference turning angle θref is set corresponding to the moving distance X of the vehicle V, the moving distance X is correctly detected even if there is a slight fluctuation in the vehicle speed during the automatic steering control. As long as the vehicle V is moving, the vehicle V always moves on the movement locus.
[0028]
Automatic steering control described above, but the driver is released when OFF the mode selecting switch S _6, if the driver in addition it has the steering wheel 1 is released when the vehicle speed exceeds a predetermined value, Return to normal power steering control.
[0029]
By the way, when the steering actuator 7 is activated during the automatic steering control, the following brake control of the steering actuator 7 is performed to prevent the ball screw mechanism 8 from hitting the limit position of the operable range and causing an impact. Done.
[0030]
In step S1 of the flowchart of FIG. 6, the vehicle speed v and the turning speed γ are read. The vehicle speed v can be calculated as a time differential value of the movement distance X calculated from the outputs of the front wheel rotation angle detection means S ₃ and S ₃ , and the turning speed γ is calculated from the output of the turning angle detection means S _1. It can be calculated as a time differential value of the turning angle θ.
[0031]
In subsequent step S2, the vehicle speed v is compared with a predetermined value (for example, 5 km / h). If the vehicle speed v is less than the predetermined vehicle speed, the process proceeds to step S7 without performing brake control of the steering actuator 7, Perform normal control. The reason is that the movement locus of the vehicle V is set as a relation of the turning angle θ with respect to the movement distance X of the vehicle V. Therefore, when the vehicle speed v decreases, the turning speed γ also decreases and the ball screw mechanism 8 can operate. This is because the possibility of an impact occurring at the limit position of the range is reduced.
[0032]
If the vehicle speed v is greater than or equal to a predetermined value in step S2, the steered speed γ is compared with a predetermined value in step S3, and if the steered speed γ is less than the predetermined value, it is determined that the possibility of an impact is low. In step S7, normal control of the steering actuator 7 is performed. On the other hand, the turning rate γ in the step S3 is shifted to step S4 equal to or greater than a predetermined value, for detecting the position of a steering rod 4 by turning state detecting means S _5.
[0033]
In step S5, it is determined whether or not the position of the steering rod 4 has approached the limit turning position. If the position has not approached the limit turning position, normal control of the steering actuator 7 is performed in step S7. If it is close to the rudder position, brake control of the steering actuator 7 is performed in step S6. This brake control is executed by turning on / off the _four transistors T _{1 to} T ₄ of the drive circuit 31 of the steering actuator 7 as already described with reference to FIG.
[0034]
Thus, when the steering speed γ is high, if the position of the steering rod 4 approaches the movement limit position and the ball screw mechanism 8 hits the moving end, a large impact may occur. Since the steering actuator 7 generates a braking force to reduce the steering speed γ, the occurrence of the impact can be avoided in advance.
[0035]
This not only prevents abnormal noise from being generated due to an impact, but also changes in the turning angle θ due to the impact and shift of the movement locus, as well as durability of the ball screw mechanism 8 and the steering actuator 7 due to the impact. Deterioration can be avoided. Since the automatic steering control by the driver steering torque to the steering wheel 1 is stopped when it is detected, the automatic steering control is canceled when the said shock steering torque detecting means S ₂ detects the pseudo steering torque However, according to the present embodiment, unnecessary stop of the automatic steering control can be avoided in advance.
[0036]
As mentioned above, although the Example of this invention was explained in full detail, this invention can perform a various design change in the range which does not deviate from the summary.
[0037]
For example, in the embodiment, the movement locus of the vehicle V up to the target position is stored in the storage unit 23 in advance, but the movement locus can be calculated from the current position and the target position of the vehicle V.
[0038]
Instead of performing the brake control of the steering actuator 7 by a short circuit of the drive circuit 31 as in the embodiment, it may be performed by flowing a braking current in the reverse direction to the steering actuator 7. That is, as shown in FIG. 7, a braking current that increases in accordance with an increase in the steering speed γ and an increase in the vehicle speed v from the time when the steering speed γ exceeds a predetermined value is set. When the vehicle approaches the limit turning position, the braking current can be added to the driving current supplied to the steering actuator 7 for automatic steering to reduce the substantial driving current and generate the braking force. It is.
[0039]
【The invention's effect】
As described above, according to the present invention, when the actuator is driven to steer the wheel during automatic steering control, the steered state of the steered mechanism that transmits the driving force of the actuator to the wheel approaches the limit steered state. Then, since the driving speed of the actuator is reduced, it is possible to avoid the occurrence of an impact on the steering mechanism in the limit steering state. Thereby, generation | occurrence | production of a hitting sound can be prevented, the shift | offset | difference of the movement locus of a vehicle can be prevented, and it becomes possible to improve the durability of an actuator and a steering mechanism.
[0040]
In particular , according to the first aspect of the invention, since the driving speed of the actuator is reduced only when the vehicle speed is equal to or higher than a predetermined value, the turning speed is generally low, so that at the time of low vehicle speed where there is no possibility of causing an impact. It is possible to avoid a reduction in the driving speed of the actuator insignificantly and to secure a more accurate movement trajectory. Further, when the vehicle speed is less than the predetermined value, the possibility that the impact is generated is low. Therefore, the reduction control of the actuator drive speed is not executed even when the steered state approaches the limit steered state.
[0041]
In particular , according to the second aspect of the invention, when the turning speed is increased to a predetermined value or more, the driving speed of the actuator is reduced. Therefore, when the turning speed is high, a large impact is likely to occur. It is possible to effectively avoid the occurrence of an impact by reducing. When the turning speed is less than a predetermined value, the impact is unlikely to occur. Therefore, even when the turning state approaches the limit turning state, the reduction control of the actuator driving speed is not executed.
[0042]
In particular, according to the invention of claim 3, since the movement locus of the vehicle is stored or calculated as the relationship of the turning angle of the wheel with respect to the movement distance of the vehicle, it is always constant even if the vehicle speed fluctuates during the automatic steering control. A movement locus can be secured.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a vehicle equipped with an automatic steering device. FIG. 2 is a diagram illustrating the operation of a back parking / left mode. FIG. 3 is a diagram showing a mode selection switch and an automatic parking start switch. FIG. 5 is a diagram showing the structure of the apparatus. FIG. 5 is a diagram showing a drive circuit of the steering actuator. FIG. 6 is a flowchart explaining the operation. FIG. 7 is an explanatory diagram of the braking current of the steering actuator according to the second embodiment of the invention. Explanation of]
7 Steering actuator (actuator)
8 Ball screw mechanism (steering mechanism)
22 Control unit (actuator control means)
23 storage unit (movement trajectory setting means)
S ₅ Steering state detection means (detection means)
V Vehicle v Vehicle speed Wf Front wheel (wheel)
X Travel distance γ Steering speed θ Steering angle

Claims (3)

A movement locus setting means (23) for storing or calculating a movement locus of the vehicle (V) to the target position, an actuator (7) for turning the wheel (Wf) via the steering mechanism (8), and a movement locus In an automatic steering apparatus for a vehicle, comprising an actuator control means (22) for controlling the drive of the actuator (7) based on the movement trajectory stored or calculated by the setting means (23),
Comprising detecting means (S ₅ ) for detecting the turning state of the turning mechanism (8),
Said actuator control means (22), wherein at detected steered state detection means (S ₅₎ executes a reduction control to reduce the driving speed of the actuator (7) when approaching the limit turning state, An automatic steering apparatus for a vehicle , wherein when the vehicle speed (v) is a low vehicle speed less than a predetermined value, the reduction control is not executed even when the steered state approaches a limit steered state . A movement locus setting means (23) for storing or calculating a movement locus of the vehicle (V) to the target position, an actuator (7) for turning the wheel (Wf) via the steering mechanism (8), and a movement locus In an automatic steering apparatus for a vehicle, comprising an actuator control means (22) for controlling the drive of the actuator (7) based on the movement trajectory stored or calculated by the setting means (23),
Comprising detecting means (S ₅ ) for detecting the turning state of the turning mechanism (8) ,
Said actuator control means (22), wherein at detected steered state detection means (S ₅₎ executes a reduction control to reduce the driving speed of the actuator (7) when approaching the limit turning state, An automatic steering apparatus for a vehicle , wherein when the turning speed (γ) is less than a predetermined value, the reduction control is not executed even when the turning state approaches a limit turning state . The movement trajectory setting means (23) stores or calculates the movement trajectory as a relationship of a turning angle (θ) of a wheel (Wf) with respect to a movement distance (X) of a vehicle (V). Item 3. The vehicle automatic steering device according to Item 1 or 2 .

Images