JP2004351999A - Automatic steering device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a steering wheel from becoming light rapidly at the moment of a switching of a control state of an actuator for turning the wheel. <P>SOLUTION: In automatic steering mode, when the steering torque applied to the steering wheel by a driver increases to a second threshold Ts, the automatic steering mode is switched to an electric power steering mode, and the driving of the actuator is controlled based on the steering torque of the driver. The second threshold Ts lies in a dead zone region lower than a first threshold Td where the actuator is driven to generate a steering assist torque in the electric power steering mode, so that the actuator does not generate the steering assist torque at the moment of the switching from the automatic steering mode to the electric power steering mode. Thus, the steering wheel is prevented from rapidly becoming light at the moment of the switching. <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 driver applies a steering torque equal to or more than a predetermined value to the steering wheel during the automatic steering mode, 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, as described in detail later with reference to FIG. 12, the above-described conventional motor generates a steering assist force until the moment when the driver operates the steering wheel to shift to the electric power steering mode during the automatic steering mode. Since the actuator that did not perform suddenly generates a steering assist force, the steering wheel suddenly became light, and the driver sometimes felt uncomfortable.
[0005]
The present invention has been made in view of the above-described circumstances, and has as its object to prevent a steering wheel from suddenly becoming lighter at the moment when a control state of an actuator for turning a wheel 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 device for a vehicle in which the driving of the vehicle is controlled, in the first control state, a region where the steering torque applied to the steering wheel by the driver is smaller than the first threshold is regarded as a dead zone, and the region equal to or larger than the first threshold is set. The driving of the actuator is controlled in the region, and in the second control state, the driver controls the operation. The actuator control means switches the second control state to the first control state when the steering torque applied to the ring handle becomes equal to or more than a second threshold value smaller than the first threshold value. There is proposed an automatic steering apparatus for a vehicle.
[0007]
According to the configuration, in the second control state in which the driving of the actuator is controlled based on the control target value stored or calculated in advance, when the steering torque applied to the steering wheel by the driver increases to the second threshold value, The control unit switches from the second control state to the first control state, and the driving of the actuator is controlled based on the steering torque applied to the steering wheel by the driver. The second threshold value at which this switching is performed is in a dead zone lower than the first threshold value at which the actuator is driven to generate the steering assist torque in the first control state. The actuator does not generate the steering assist torque at the moment when the control is switched from the control state to the first control state. As a result, it is possible to prevent the steering wheel from suddenly becoming lighter at the moment of switching from the second control state to the first control state, and to prevent the driver from feeling uncomfortable.
[0008]
According to a second aspect of the invention, in addition to the configuration of the first aspect, the control target value is stored or calculated in advance as a vehicle movement path from a movement start position to a target vehicle position. An automatic steering device for a vehicle is proposed.
[0009]
According to the above configuration, the control target value for controlling the driving of the actuator in the second control state is stored or calculated in advance as the vehicle movement path from the movement start position to the target vehicle position. The steering for moving the vehicle from the movement start position to the target vehicle position can be automatically performed using an actuator for assisting the vehicle.
[0010]
According to a third aspect of the invention, in addition to the configuration of the second aspect, the control target value is set as a constant wheel steering angle that can guide the vehicle to a target vehicle position. An automatic steering device for a vehicle is proposed.
[0011]
According to the above configuration, the control target value for controlling the driving of the actuator in the second control state is a constant wheel turning angle that can guide the vehicle to the target vehicle position. Control can be simplified.
[0012]
According to the fourth aspect of the invention, in addition to the configuration of the second aspect, the control target value is set as a wheel steering angle that changes according to a moving distance of the vehicle to a target vehicle position. An automatic steering device for a vehicle characterized by the following is proposed.
[0013]
According to the above configuration, the control target value for controlling the driving of the actuator in the second control state is the wheel turning angle that changes according to the moving distance of the vehicle to the target vehicle position. The movement locus of the vehicle to the vehicle position can be set freely.
[0014]
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 target turning angle δ 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.
[0015]
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.
[0016]
1 to 13 show an embodiment of the present invention. FIG. 1 is an overall configuration diagram of a steering device of a vehicle, FIG. 2 is an operation explanatory diagram when the vehicle is moved backward to a parking space, and FIG. FIG. 4 is an explanatory diagram of an operation in the case of turning back in the process of moving the vehicle backward, FIG. 4 is an explanatory diagram of the yaw angle θ of the vehicle, FIG. 5 is an explanatory diagram of the moving distance L of the vehicle, and FIG. 7 to 9 are diagrams for explaining the effect of left-back parking, FIG. 10 is a graph showing a relationship between the steering torque and the assist torque, and FIG. 11 is a diagram showing the relationship between the steering torque and the presence or absence of the assist. FIG. 12 is a graph showing a change, FIG. 12 is a graph illustrating an operation when the first threshold is set smaller than the second threshold, and FIG. 13 is an operation when the first threshold is set larger than the second threshold. It is a graph explaining.
[0017]
As shown in FIG. 1, a pinion 13 is provided at a lower end of a steering shaft 12 that rotates integrally with a steering handle 11 operated by a driver, and a steering rod 15 integrally formed with a rack 14 that meshes with the pinion 13. Are connected to left and right front wheels Wf, Wf via tie rods 16, 16, respectively. An actuator 17 composed of an electric motor is connected to a lower portion of the steering shaft 12 via a worm gear mechanism 18.
[0018]
The electronic control unit U includes a start switch 19 for instructing the start of parking assistance, a steering torque sensor Sa for detecting a steering torque input to the steering handle 11, and a rotation of the front wheels Wf, Wf based on the steering angle of the steering handle 11. The steering angle sensor Sb for detecting the steering angle, the brake sensor Sc for detecting the operation amount of the brake pedal 20, the accelerator sensor Sd for detecting the operation amount of the accelerator pedal 21, and the shift position selected by the shift lever 22 A shift position sensor Se for detecting, a vehicle speed sensor Sf for detecting a vehicle speed from the rotational speeds of the front wheels Wf, Wf, a moving distance sensor Sg for detecting a moving distance of the vehicle from an integrated value of the rotational speeds of the front wheels Wf, Wf, Is connected to a yaw rate sensor Sh that detects the yaw rate of the vehicle. Inside the electronic control unit U, a target turning angle setting means 23 for setting a target turning angle δ when performing parking assistance is provided. It should be noted that since the moving distance of the vehicle can be calculated by integrating the vehicle speed detected by the vehicle speed sensor Sf with time, the moving distance sensor Sg can be omitted in that case.
[0019]
When the start switch 19 is off, a normal electric power steering mode is set, and a steering torque generated when the driver operates the steering handle 11 is detected by the steering torque sensor Sa, and the actuator 17 is moved in a direction in which the steering torque decreases. To generate an assist torque to assist the driver in operating the steering handle 11. At this time, when the vehicle speed detected by the vehicle speed sensor Sf is high, the assist torque generated by the actuator 17 is reduced to improve the straight running stability of the vehicle. When the vehicle speed detected by the vehicle speed sensor Sf is low, the actuator 17 is activated. By increasing the generated assist torque, the operating force of the steering handle 11 at the time of stationary steering or the like can be reduced.
[0020]
When the start switch 19 is turned on, when the predetermined condition is satisfied, the electric power steering mode is switched to the automatic steering mode, and the steering wheel 11 is moved by the actuator 17 without the driver operating the steering wheel 11. Operated automatically.
[0021]
Specifically, when the vehicle V is stopped at the position shown in FIG. 2A and the start switch 19 is turned on, the actuator 17 is operated, and the front wheels Wf and Wf are steered to the left. When the turning angle of the front wheels Wf, Wf detected by the turning angle sensor Sb reaches the target turning angle δ (here, the full turning angle) set by the target turning angle setting means 23, the actuator 17 stops. From the automatic steering mode to the electric power steering mode. As described above, the actuator 17 operates the steering handle 11 instead of the driver, so that the operation burden on the driver is reduced. After returning from the automatic steering mode to the electric power steering mode, the driver may finely adjust the position of the steering wheel 11 to move the vehicle V backward to the parking space.
[0022]
In order to set the automatic steering mode, in addition to turning on the start switch 19, when the vehicle V is stopped (including the case where the vehicle speed is extremely low), the driver turns the steering wheel 11 It is necessary to be not operating. The former condition is that the vehicle speed detected by the vehicle speed sensor Sf is equal to or lower than a predetermined value, the operation amount of the brake pedal 20 detected by the brake sensor Sc is equal to or higher than a predetermined value, and the acceleration of the accelerator pedal 21 detected by the accelerator sensor Sd. It is assumed that all or part of the operation amount is equal to or less than the predetermined value is satisfied. The latter condition is satisfied when the steering torque detected by the steering torque sensor Sa is equal to or less than a predetermined value. If the vehicle enters the automatic steering mode when the vehicle speed is equal to or lower than a predetermined value (for example, equal to or lower than 5 km / h), the stationary operation is not performed, so that the power consumption of the actuator 17 can be reduced.
[0023]
By the way, considering a case where the driver temporarily stops the vehicle V and then parks in the reverse direction, as shown in FIG. 2A, the inclination of the vehicle V with respect to the passage is small, and the direction of the vehicle V does not change by approximately 90 ° in the reverse direction. If the vehicle cannot be parked in the parking space, the steering wheel 11 is normally fully steered. However, as shown in FIG. 2 (b), when the vehicle V is inclined to a certain extent with respect to the passage, the vehicle turns too much when fully steered, so that an appropriate steering angle smaller than full steering is set. There is a need. Further, when the vehicle reverses once after turning back, as shown in FIG. 2 (c), the steering wheel 11 is slightly inclined because it is almost tilted toward the parking space.
[0024]
In the case of turning back and moving forward, as in the case of reverse driving, as shown in FIG. 3 (a), when the inclination with respect to the passage is not so large, the steering wheel 11 is turned to full steering and the vehicle moves forward. To increase the slope. As shown in FIG. 3B, when the steering wheel 11 is already inclined, it is not necessary to turn the steering handle 11 until the vehicle is fully steered. As shown in FIG. 3 (c), when the vehicle is tilted almost to the direction of the parking space, it is sufficient to move forward without turning the steering handle 11.
[0025]
Therefore, in the present embodiment, the yaw angle θ of the vehicle V is detected, and the target turning angle δ is set based on the yaw angle θ. As shown in FIG. 4, in the electric power steering mode, when the current vehicle position is P1 and the reference position passed past the vehicle position P1 by the moving distance L in the past is P0, the yaw of the reference position P0 is The yaw angle θ of the current vehicle position P1 is calculated based on the angle θ (θ = 0). The yaw angle θ is sequentially updated each time the vehicle V moves forward by a predetermined distance (for example, 10 cm) and the vehicle position P1 changes. The magnitude of the moving distance L is defined as the minimum turning radius Rm of the vehicle V. As is clear from FIG. 5, if the moving distance L is the minimum turning radius Rm of the vehicle V, the vehicle V can be correctly moved to the parking space by moving backward from the current vehicle position P1 in a fully steered state. . The moving distance L of the vehicle V is detected by the moving distance sensor Sg, and the yaw angle θ is detected by integrating the yaw rate detected by the yaw rate sensor Sh.
[0026]
Next, the operation of the present system will be described. Here, left-back parking in which the vehicle V is parked in the parking space on the left side of the aisle will be described as an example.
[0027]
First, as shown in FIG. 7, the driver moves the vehicle V straight along the passage and passes in front of the parking space. At this time, the vehicle V faces the direction along the passage in front of the parking space. That is, as shown in FIG. 7, when the vehicle V is traveling straight along the passage from before the reference position P0, the direction line of the reference yaw angle at the reference position P0 is substantially parallel to the passage, and is traveling straight. Therefore, the yaw angle θ at the vehicle position P1 is 0, that is, parallel to the path similarly to the reference yaw angle at the reference position P0. This also means that it is perpendicular to the parking space, ie 90 °.
[0028]
After the driver advances the vehicle V along the passage and passes through the parking space, the driver steers the front wheels Wf and Wf to the right and turns the vehicle V to the right to park on the left side of the passage as shown in FIG. While tilting, the vehicle V is stopped at a position where the vehicle has passed the parking space L by eye. At this time, the reference position P0 is located at the vehicle position P1 in FIG. 7, that is, substantially in front of the parking space. As described above, since the vehicle V is passed along the path at this position, the direction of the reference yaw angle (θ = 0) at the reference position P0 is substantially parallel to the path. Therefore, the yaw angle θ at the stopped vehicle position P1 substantially matches the inclination with respect to the direction of the passage, and in order to park in the parking space, the yaw angle θ only needs to be inclined at a right angle, that is, 90 °. . In FIG. 8, when the start switch 19 is turned on in a state where the shift position sensor Se detects that the shift lever 22 has been operated to the R position in order to stop at the parking space from the vehicle position P1 in the reverse direction, The target turning angle setting means 23 of the electronic control unit U calculates the target turning angle δ. The start switch 19 may be omitted by using the detection of the shift position sensor Se that the shift lever 22 has been operated to the R position as a system start signal.
[0029]
In FIG. 6, as the yaw angle θ increases from 0 ° to 90 °, the target turning angle δ decreases from the full turning angle to 0. When the yaw angle θ is rightward, it is determined that the parking space is on the left side of the passage, and the direction of the target turning angle δ is left turning. Conversely, when the yaw angle θ is to the left, it is determined that the parking space is on the right side of the passage, and the direction of the target turning angle δ is right turning.
[0030]
In FIG. 8, since θ is rightward, it is determined that the parking space is on the left, and the direction of the target turning angle δ is left turning. In addition, since the yaw angle θ = θa is small and the vehicle V must be further tilted to the yaw angle θ = 90 ° when the vehicle is parked in the back, the full turning is set as the target turning angle δ as shown in FIG. You. Then, the steering handle 11 is automatically rotated by the actuator 17 so that the steering angle matches the full steering. After the steering angle is fully steered, the driver reverses the vehicle V while finely adjusting the angle of the steering handle 11 as necessary. As described above, L is the minimum turning radius Rm of the vehicle V as described above. Therefore, the vehicle V is guided to the parking space. When the vehicle is stopped in the parking space and the shift lever 22 is set to the P position, the automatic steering mode is released and the vehicle returns to the electric power steering mode.
[0031]
In the case where the width of the passage is wide and the yaw angle θ of the vehicle V can be greatly inclined (θ = θb), for example, as shown in FIG. As shown in FIG. 6, by setting the target turning angle δ to an appropriate value δb smaller than full turning, it is possible to prevent excessive turning.
[0032]
As described above, by setting the target turning angle δ for controlling the driving of the actuator 17 in the automatic steering mode to a constant value that can be guided to the parking space only by moving the vehicle V backward, the target turning angle δ Setting and control of the actuator 17 can be simplified.
[0033]
FIG. 10 is a graph showing the assist characteristics of the electric power steering device. In the dead zone where the steering torque Th input to the steering wheel 11 by the driver is less than the first threshold value Td, the assist torque Ta by the actuator 17 is not generated, and When the steering torque Th becomes equal to or greater than the first threshold value Td, the assist torque Ta linearly increases. Accordingly, as shown in FIG. 11, in a region where the steering torque Th input to the steering handle 11 by the driver is equal to or greater than the first threshold value Td, the steering torque Th of the driver is reduced by the assist torque Ta generated by the actuator 17. , Light steering operation becomes possible.
[0034]
By the way, when the driver finds an obstacle in a parking space or gives up parking and operates the steering handle 11 while the front wheels Wf and Wf are being steered in the automatic steering mode, the electric power is switched from the automatic steering mode. The mode is switched to the steering mode so that the actuator 17 does not hinder the steering operation of the driver. Further, even if the driver accidentally touches the steering wheel 11 while the front wheels Wf, Wf are being steered in the automatic steering mode, it is necessary to prevent the automatic steering mode from being stopped against the driver's will. Therefore, if the steering torque input to the steering wheel 11 is less than the second threshold value Ts, the automatic steering mode is not switched to the electric power steering mode. If the steering torque becomes equal to or more than the second threshold value Ts, the automatic steering mode is switched. To the electric power steering mode.
[0035]
As shown in FIG. 12, assuming that the second threshold value Ts is set to be larger than the first threshold value Td, the steering torque Th applied by the driver to the steering wheel 11 in the automatic steering mode exceeds the first threshold value Td. Even if it is increased, the assist torque is not generated by the actuator 17 in the automatic steering mode, so that the steering torque Th increases to the second threshold value Ts (see the solid line). As a result, when switching from the automatic steering mode to the electric power steering mode at the point a where the steering torque Th becomes equal to or more than the second threshold value Ts, the steering torque Th becomes the electric power steering mode in the electric power steering mode in which the actuator 17 generates the assist torque. Since the value suddenly decreases to the value (see the broken line), the driver feels that the steering wheel 11 has suddenly become lighter and feels strange.
[0036]
On the other hand, in the present embodiment, as shown in FIG. 13, since the second threshold value Ts is set smaller than the first threshold value Td, the steering torque Th applied to the steering wheel 11 by the driver in the automatic steering mode is reduced. Even if the steering torque Th is increased to exceed the second threshold value Ts at the point b and is switched from the automatic steering mode to the electric power steering mode, the steering torque Th increases linearly without a sudden change. When the steering torque Th reaches the first threshold value Td at the point c, the assist by the actuator 17 is started by exiting the dead zone in the electric power steering mode.
[0037]
As described above, the second threshold value Ts for switching from the automatic steering mode to the electric power steering mode is set to be smaller than the first threshold value Td of the steering torque Th at which the actuator 17 generates the assist torque Ta. When the mode is switched to the electric power steering mode, the steering torque Th can be prevented from sharply decreasing, and the driver can be prevented from feeling uncomfortable by feeling that the steering handle 11 has suddenly become lighter.
[0038]
Although the embodiments of the present invention have been described in detail, various design changes can be made in the present invention without departing from the gist thereof.
[0039]
For example, in the embodiment, the target turning angle δ in the automatic steering mode is set to a value that can guide the vehicle V to the parking space at a constant turning angle. The target turning angle δ in the automatic steering mode can be set as a value that changes according to the moving distance of the vehicle V from the parking start position to the parking space. Thereby, the movement locus of the vehicle V from the parking start position to the parking space can be set to an arbitrary locus other than the arc.
[0040]
【The invention's effect】
According to the first aspect of the present invention, the steering torque applied to the steering wheel by the driver in the second control state in which the driving of the actuator is controlled based on the control target value stored or calculated in advance. Is increased to a second threshold value, the actuator control means switches from the second control state to the first control state, and the driving of the actuator is controlled based on the steering torque applied to the steering wheel by the driver. The second threshold value at which this switching is performed is in a dead zone lower than the first threshold value at which the actuator is driven to generate the steering assist torque in the first control state. The actuator does not generate the steering assist torque at the moment when the control is switched from the control state to the first control state. As a result, it is possible to prevent the steering wheel from suddenly becoming lighter at the moment of switching from the second control state to the first control state, and to prevent the driver from feeling uncomfortable.
[0041]
According to the second aspect of the present invention, the control target value for controlling the driving of the actuator in the second control state is stored or calculated in advance as a movement path of the vehicle from the movement start position to the target vehicle position. Therefore, the steering for moving the vehicle from the movement start position to the target vehicle position can be automatically performed by using the actuator for assisting the steering torque of the driver.
[0042]
According to the third aspect of the present invention, since the control target value for controlling the driving of the actuator in the second control state is a constant wheel turning angle that can guide the vehicle to the target vehicle position, The setting of the control target value and the control of the actuator can be simplified.
[0043]
According to the invention described in claim 4, the control target value for controlling the driving of the actuator in the second control state is the wheel steering angle that changes according to the moving distance of the vehicle to the target vehicle position. Therefore, the movement locus of the vehicle from the control start position to the target vehicle position can be set freely.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a vehicle steering system according to a first embodiment; FIG. 2 is an operation explanatory diagram when the vehicle is moved backward to a parking space; FIG. 3 is turned back in the process of moving the vehicle backward; FIG. 4 is an explanatory diagram of the yaw angle θ of the vehicle. FIG. 5 is an explanatory diagram of the moving distance L of the vehicle. FIG. 6 is a diagram showing the relationship between the yaw angle θ of the vehicle and the target turning angle δ. FIG. 7 is a diagram for explaining the operation of left-back parking. FIG. 8 is a diagram for explaining the operation of left-back parking. FIG. 9 is a diagram for explaining the operation of left-back parking. FIG. 10 is a graph showing the relationship between steering torque and assist torque. 11 is a graph showing a change in steering torque depending on the presence or absence of assist. [FIG. 12] A graph for explaining an operation when the first threshold is set smaller than the second threshold. [FIG. 13] A first threshold is set to the second threshold. Graph explaining the operation when the value is set to be larger than the threshold value
Th steering torque Td first threshold value Ts second threshold value U electronic control unit (actuator control means)
V Vehicle Wf Front wheel (wheel)
11 Steering handle 17 Actuator δ Target turning angle (Target control value)

Claims (4)

An actuator (17) for steering a wheel (Wf) of the vehicle (V), and an actuator control means (U) for switching the actuator (17) between a first control state and a second control state;
In the first control state, the driving of the actuator (17) is controlled based on the steering torque (Th) applied to the steering handle (11) by the driver,
In the second control state, in an automatic steering device for a vehicle in which driving of an actuator (17) is controlled based on a control target value (δ) stored or calculated in advance,
In the first control state, a region where the steering torque (Th) applied to the steering wheel (11) by the driver is smaller than the first threshold (Td) is defined as a dead zone, and a region where the steering torque (Th) is equal to or larger than the first threshold (Td). Is controlled to drive the actuator (17),
In the second control state, when the steering torque (Th) applied to the steering wheel (11) by the driver becomes equal to or greater than a second threshold (Ts) smaller than the first threshold (Td), the actuator control is performed. The means (U) switches the second control state to the first control state. 2. The automatic steering apparatus for a vehicle according to claim 1, wherein the control target value (δ) is stored or calculated in advance as a movement path of the vehicle (V) from a movement start position to a target vehicle position. 3. 3. The automatic steering apparatus for a vehicle according to claim 2, wherein the control target value ([delta]) is set as a constant wheel turning angle capable of guiding the vehicle (V) to a target vehicle position. The automatic steering apparatus for a vehicle according to claim 2, wherein the control target value (?) Is set as a wheel steering angle that changes according to a moving distance of the vehicle (V) to a target vehicle position. .

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