JP2006182055A - Steering control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering control device for a vehicle capable of normally finishing a steer-by-wire system. <P>SOLUTION: This steering control device is furnished with a steering control means (step S6) to drive and control at least either an actuator 4 for turning to add turning torque to a steering tire 3 or an actuator 2 for steering reaction force to add steering force to a steering wheel 1, a power stopping judgement means (step S1) to judge whether a power source of the vehicle is stopped or not, a tire input detection means (step S3) to detect tire input from a road surface and a steering control stopping means (step S5) to stop steer-by-wire control when power stopping of the vehicle is judged and a state where the tire input does not change continues for a specified period of time Ts. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to the technical field of a vehicle steering control device that is employed in a steer-by-wire system or the like in which there is no mechanical connection between a steering side having a steering wheel and a steered side having a steered tire.

Conventionally, in steer-by-wire (SBW) systems that acquire vehicle speed information via an ABS controller, the drive power supply to the SBW controller is turned off only when the ignition switch is turned off and the vehicle speed is detected as zero. It is the composition to do. As a result, even if the ignition switch is turned off during traveling, power supply to the ABS controller is not stopped until the vehicle speed becomes zero, so the SBW controller can acquire vehicle speed information from the ABS controller. SBW control can be continued safely (see, for example, Patent Document 1).
JP 2004-168258 A

  However, in the above prior art, for example, if vehicle speed information is lost due to the occurrence of an in-vehicle network abnormality or the like, the vehicle speed information cannot be obtained, and thus steering control is terminated by turning off the ignition switch during traveling. Alternatively, there is a possibility that a problem such as the steering control not being ended even if the ignition switch is turned off during parking.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a vehicle steering control device capable of normally ending steering control.

In order to achieve the above object, the present invention provides:
Steering control means for driving and controlling at least one of steering means for adding steering torque to the steering wheel and steering reaction force means for adding steering force to the steering wheel;
Power stop determining means for determining whether or not the power source of the vehicle stops;
Tire input detection means for detecting input from the road surface to the tires of the vehicle;
A steering control stop means for stopping the steering control when it is determined that the power of the vehicle is stopped and the tire input does not change for a predetermined time;
It is characterized by providing.

  In the present invention, when the power source of the vehicle is stopped and no input from the road surface continues for a predetermined time, it is determined that the vehicle is stopped and the steering control is terminated. In other words, since the steering control is stopped only when the vehicle is surely stopped for a predetermined time or longer, the steering control stop during traveling can be prevented.

  Hereinafter, the best mode for carrying out the present invention will be described based on Examples 1 and 2.

First, the configuration will be described.
FIG. 1 is a diagram illustrating a configuration of a steer-by-wire (SBW) system according to the first embodiment.
In the SBW system shown in the first embodiment, there is a mechanical connection between the steering wheel 1 and the steering reaction force actuator (steering reaction force means) 2 and the steered tire 3 and the steering actuator (steering means) 4. No.

  This SBW system achieves the turning operation by driving the turning actuator 4 based on the command value calculated by the turning controller 6 in accordance with the rotation operation of the steering wheel 1. The steering actuator 4 can be composed of an electric motor 4a such as a brushless motor.

  The steering reaction force actuator 2 for applying a steering reaction force to the handle 1 can be constituted by an electric motor 2 a such as a brushless motor, as with the steering actuator 4. The steering reaction force actuator 2 is driven based on a command value calculated by the steering reaction force controller 5.

  The command values calculated by the steering reaction force controller 5 and the steering controller 6 are current command values to the electric motors constituting the steering reaction force actuator 2 and the steering actuator 4. Each signal is transmitted through the communication line 7 between the steering reaction force controller 5 and the steering controller 6, and the communication line 7 has a double system configuration.

  In addition, sensors (such as a motor rotation angle sensor) that detect the operating states of the steering reaction force actuator 2 and the steering actuator 4 have a double system configuration, and realize a redundant configuration as an SBW system. .

  The SBW system configured as described above starts to operate when the ignition switch 8 is turned on. Further, in the first embodiment, the termination of the SBW system is configured so that the SBW system is not immediately terminated when the ignition switch 8 is turned off in consideration of safety when the ignition switch 8 is accidentally turned off during traveling. . The SBW system is terminated after it is determined that the vehicle is surely stopped and the driver is releasing the handle 1.

Next, the operation will be described.
[Steering control processing]
FIG. 2 is a flowchart showing the flow of the steering control process executed by the steering reaction force controller 5 and the steering controller 6 of the first embodiment, and each step will be described below. This process is executed at a predetermined control cycle (for example, 5 msec).

  In step S1, the state of the IGN signal output from the ignition switch 8 is checked (corresponding to power stop determination means). When the IGN signal is on, the process proceeds to step S6, and when it is off, the process proceeds to step S2.

  In step S2, the current flowing through the steering reaction force motor 2a of the steering reaction force actuator 2 is checked (corresponding to hand release detection means). As the steering reaction force motor current value, either a steering reaction force motor current command value calculated by the steering reaction force controller 5 or a value obtained by actually detecting the steering reaction force motor current may be used. If the absolute value of the steering reaction force motor current value obtained here is equal to or greater than a predetermined release current threshold Ih, it is determined that the driver is steering, that is, the handle 1 is being held, and the process proceeds to step S6. If the absolute value of the steering reaction motor current value is less than the release current threshold Ih, it is determined that the driver is not steering, that is, the hand is released from the handle 1, and the process proceeds to step S3. To do.

  Here, the hand release current threshold value Ih is a sufficiently small value. When the absolute value of the steering reaction force motor current is smaller than the hand release current threshold value Ih, no torque is applied to the handle 1. I can judge. In the first embodiment, the steering reaction force motor current is used to determine whether the driver has released his hand from the handle 1, but based on the steering torque detected or estimated by a torque sensor or the like installed on the steering column shaft. You may judge (equivalent to a steering torque detection means).

  In step S3, the current flowing through the steering motor 4a of the steering actuator 4 is checked (corresponding to tire input detection means). As the steered motor current value, either the steered motor current command value calculated by the steered controller 6 or a value obtained by actually detecting the steered motor current may be used. If the absolute value of the steered motor current obtained here is equal to or greater than the vehicle stop current threshold Is, it is determined that an axial force change has occurred in the steering rack, that is, the vehicle is running, step S6. If the absolute value of the steering motor current is less than the vehicle stop current threshold Is, it is determined that there is no change in axial force in the steering rack, that is, the vehicle is stopped, and the step The process proceeds to S4.

  Here, the vehicle stop current threshold value Is is such that the absolute value of the steering motor current is greater than the vehicle stop current threshold value Is when the vehicle is running even if the driver releases the handle 1. Is set to a sufficiently small value so that the In the first embodiment, the stop state of the vehicle is determined using the steered motor current, but is detected or estimated by an axial force sensor that detects the force generated on the steering rack shaft, and is determined based on the steering rack axial force. You may do it.

  In step S4, the OFFtimer is checked for a time period in which the absolute value of the steering reaction force motor current is less than the release current threshold value Ih and the state where the absolute value of the steering motor current is less than the vehicle stop current threshold value Is is continued. If the OFFtimer is equal to or longer than the predetermined time Ts, the process proceeds to step S5. If the OFFtimer is less than the predetermined time Ts, the process proceeds to step S6. A state in which the IGN signal is off, the absolute value of the steering reaction force motor current is less than the release current threshold Ih, and the absolute value of the steering motor current is less than the vehicle stop current threshold Is is a predetermined time Ts (for example, 15 seconds) ) If it continues, it is determined that the driver has released his hand from the steering wheel 1 and the vehicle is stopped.

  In step S5, the SBW system is terminated (corresponding to steering control stop means). The steering controller 6 finishes outputting the current command value to the steering motor 4a, and the steering reaction force controller 5 finishes outputting the current command value to the steering reaction force motor 2a.

  In step S6, normal SBW control, that is, the steering controller 6 outputs a current command value to the steering motor 4a, and the steering reaction force controller 6 outputs a current command value to the steering reaction force motor 2a ( Equivalent to steering control means).

[Technical background]
In today's networking of vehicle control systems, the steer-by-wire (SBW) system does not always receive the vehicle speed signal detected by the vehicle speed sensor directly from the vehicle speed sensor. Vehicle speed information may be obtained from other control systems via the. In the steering control device having such a configuration, for example, when the ignition switch is switched from on to off by a driver or the like, the vehicle is generally assumed to be stopped, that is, the vehicle is parked. Since the control system is configured, after the ignition switch is turned off, the drive power supplied to the entire system including other systems that generate vehicle speed information (for example, ABS system) is generally cut off. Has been adopted.

  As described above, according to the steering control device configured to acquire the vehicle speed information from the other system, the driving power supplied to the other system is also cut off after the ignition switch is turned off. Vehicle speed information cannot be obtained from the system.

  In order to solve these problems, in the vehicle steering apparatus described in Japanese Patent Application Laid-Open No. 2004-168258, vehicle speed information is acquired from an SBW controller that detects an OFF state of an ignition switch and outputs an OFF notification, and a wheel speed sensor. And an ABS controller that outputs vehicle speed zero information when it is detected that the vehicle speed is zero. The ABS controller is configured to stop the supply of driving power from the battery only when the ignition switch OFF notification is output from the SBW controller and the vehicle speed of the vehicle is zero. Thus, even when the ignition switch is turned off during traveling, vehicle speed information can be acquired from the ABS controller, and SBW control can be safely continued (FIG. 3).

However, in the above prior art, for example, when the vehicle speed information is lost due to the occurrence of an in-vehicle network abnormality or the like, the following problems may occur.
(a) As shown in FIG. 4, when the vehicle speed is erroneously recognized as zero during traveling, the power supply to the ABS system stops when the ignition switch is turned off, so the SBW system cannot obtain vehicle speed information. .
(b) As shown in FIG. 5, if the vehicle speed is erroneously recognized as other than zero during parking, the SBW system is not terminated and the battery power is consumed even though the ignition switch is turned off.

  In general, in the SBW system, the vehicle speed information is not configured redundantly, unlike the steering control related information, considering its importance. Therefore, a redundant configuration such as reading the vehicle speed sensor signal directly with a separate SBW controller leads to an increase in cost.

[SBW system termination judgment action]
On the other hand, in the SBW system of the first embodiment, when the ignition switch 8 is turned off, the driver releases his hand from the steering wheel 1 and no input from the road surface continues for a predetermined time Ts or longer, the vehicle Judge that it is stopped and terminate the SBW system.

  That is, the state where the ignition switch is turned off, the absolute value of the steering reaction force motor current is less than the let-off current threshold value Ih, and the absolute value of the steering motor current is less than the vehicle stop current threshold value Is, If it is equal to or longer than the predetermined time Ts, in the flowchart of FIG. 2, the process proceeds from step S1, step S2, step S3, step S4, and step S5. In step S5, the SBW system is terminated.

  Therefore, only when the engine is stopped, the handle 1 is not gripped, and the steered tire 3 is not steered continues for a predetermined time Ts, that is, only when the vehicle is surely stopped. Since the system is terminated, it is possible to prevent the SBW system from stopping while driving. In addition, the steering control related information (steering reaction force motor current, steering motor current) used for vehicle stop determination is highly important in the SBW system and has a redundant configuration (double system or more). The signal does not become abnormal due to failure. Therefore, it is possible to terminate the SBW system normally without increasing the cost.

[Tire input change detection action based on steering motor current change]
In Example 1, the tire input change is detected from the rack axial force change. During traveling, since force from the road surface is received through the steered tire 3 even when traveling straight, it can be determined that the vehicle is traveling when an axial force exceeding a predetermined value is generated.

  Moreover, the rack axial force change is calculated | required from the change of the electric current which flows into the steering motor 4a. A current command value for making the actual turning angle coincide with the turning angle command value is input to the turning motor 4a. That is, even in straight traveling (zero turning angle), the current actually flowing to the motor constantly changes during traveling in order to compensate for disturbances from the road surface. Therefore, by monitoring the change state of the current value including the influence from the road surface, a value corresponding to the change in the axial force generated on the rack shaft can be obtained.

[Hand release detection action based on steering reaction force motor current change]
In the first embodiment, it is detected from the steering torque of the driver whether or not the driver has released his hand from the handle 1. Since the steering torque is always generated in the steering wheel 1 when the driver is gripping the steering wheel 1, the SBW system is not terminated while the torque is generated. As a result, even if the engine is stopped, not only SBW control but also steering assist control (EPS control) can be continued, and it is possible to cope with stationary after engine stop.

  Further, the steering torque is obtained from the change in the current flowing through the steering reaction force motor 2a that generates the steering reaction force torque. The steering reaction force motor 2a receives a current command value calculated according to a steering angle, a steering angular velocity, and a differential value (steering angular acceleration) of the steering angular velocity. That is, when the driver is gripping the steering wheel 1, the steering angle, the steering angular velocity, and the differential value of the steering angular velocity change, so the value of the current flowing through the steering reaction force motor 2a always changes. Therefore, by monitoring the current change of the steering reaction force motor 2a, it can be reliably determined whether or not the driver is holding the steering wheel 1.

Next, the effect will be described.
In the vehicle steering control device according to the first embodiment, the following effects can be obtained.

  (1) Steering control means for drivingly controlling at least one of the steering actuator 4 for applying steering torque to the steered tire 3 and the steering reaction force actuator 2 for applying steering force to the steering wheel 1 (step S6) ), Power stop determination means (step S1) for determining whether or not the power source of the vehicle is stopped, tire input detection means (step S3) for detecting tire input from the road surface, and determination of whether the power of the vehicle is stopped And a steering control stop means (step S5) for stopping the steer-by-wire control when the state where the tire input does not change continues for a predetermined time Ts, so that the vehicle is reliably stopped. The steer-by-wire system is stopped only when it has continued for a certain period of time. Always it is terminated.

  (2) Provided with hand release detecting means (step S2) for detecting whether or not the driver has released his / her hand from the steering wheel, and the steering control stop means, when the hand released state continues for a predetermined time Ts or longer, steer-by-wire Stop control. That is, even when the vehicle is stopped, if the driver is holding the steering wheel 1, the steer-by-wire control is not stopped, so that the vehicle is operated in response to the stationary operation after the engine is stopped. The direction tire 3 can be steered.

  (3) Steering torque detection means for detecting the steering torque input to the handle 1 is provided, and the release control means determines that it is in the release state when the state where the steering torque does not change continues for a predetermined time Ts. The state can be determined reliably.

  (4) Since the hand release detection means detects the change in the steering torque based on the change in the current flowing through the steering reaction force motor 2a, the change in the steering torque can be detected more accurately. Further, since the sensor for detecting the steering reaction force motor current has a redundant configuration with a double system, it is possible to detect the hand-off state even when a primary failure occurs. Therefore, the reliability of the system can be improved without increasing the cost as compared with the conventional technique using the vehicle speed signal.

  (5) Since the tire input detection means detects the tire input change from the rack axial force change, it can reliably determine whether or not the vehicle is traveling.

  (6) The tire input detection means detects a change in the rack axial force based on a change in the current flowing through the steering motor 4a, and the sensor for detecting the steering motor current has a dual redundant configuration. Therefore, even when a primary failure occurs, it can be detected whether or not the vehicle is running. Therefore, the reliability of the system can be improved without increasing the cost, as compared with the conventional technique for determining the vehicle stop using the vehicle speed signal.

  Example 2 is a power assist control that activates a backup mechanism that connects a steering wheel and a steered tire when a driver's vehicle stop instruction is detected, and assists the driver's steering using a steering actuator. Is an example of

First, the configuration will be described.
FIG. 7 is a diagram illustrating a configuration of a steer-by-wire (SBW) system according to the second embodiment. A mechanical backup mechanism 9 is provided between the steering wheel 1 and the steered tire 3 with respect to the configuration of the first embodiment. The difference is that power assist control is performed after the engine is stopped.

  The mechanical backup mechanism 9 mechanically connects the steering reaction force actuator 2 and the steering actuator 4 with a cable or the like, for example, and steers or disengages the clutch 10 to steer the handle 1. It is possible to connect and disconnect the mechanical connection with the tire 3.

  Engagement / release of the clutch 10 is controlled by a steering controller 6. The steering controller 6 releases the clutch 10 during the SBW control. When the SBW system fails, the steering controller 6 engages the clutch 10 and operates the mechanical backup mechanism 9. This enables steering when the SBW system fails.

  In the SBW system of the second embodiment, when the ignition switch 8 is turned off and the driver is holding the handle 1, the clutch 10 is engaged to operate the mechanical backup mechanism 9, and the steering actuator 4 performs power assist control for reducing the driver's steering burden.

Next, the operation will be described.
[Steering control processing]
FIG. 8 is a flowchart showing the flow of the steering control process executed by the steering reaction force controller 5 and the steering controller 6 of the second embodiment. Each step will be described below. This process is executed at a predetermined control cycle (for example, 5 msec). Steps S1, S3 to S6 are the same steps as steps S1, S3 to S6 in FIG.

  In step S2, the current flowing through the steering reaction force motor 2a of the steering reaction force actuator 2 is checked. If the absolute value of the steering reaction force motor current value is equal to or greater than a predetermined release current threshold Ih, the driver When it is determined that the steering wheel 1 is being gripped and the process proceeds to step S7 and the absolute value of the steering reaction force motor current value is less than the release current threshold value Ih, the handle 1 is released. Judge, and go to step S3.

  In step S7, the clutch 10 of the mechanical backup mechanism 9 is engaged, and the process proceeds to step S8.

  In step S8, the battery voltage is confirmed, and the process proceeds to step S9. If power assist control is continued with the engine stopped, battery power is consumed. Therefore, the battery voltage is checked in order to execute or stop the power assist control according to the state of the battery.

  In step S9, power assist control is performed using the torque generated by the steering motor 4a. Steps S9 and S8 constitute power assist control means.

  As the power assist control, for example, as in the technique described in Japanese Patent Application Laid-Open No. 11-34892, the target current supplied to the assist motor is calculated based on the steering torque signal, and the current value actually flowing to the assist motor is detected. Then, a drive control signal is supplied to the assist motor based on the deviation between the two. A method has been proposed in which the drive control signal is gradually reduced with the passage of time when the ignition switch 8 is turned off and when the power supply voltage of the battery stops below a predetermined voltage. Here, the predetermined voltage of the battery means, for example, about 8V before the engine is stopped.

  The power assist control is performed by the steering controller 6, and the steering reaction force controller 5 performs a process of ending the current command value to the steering reaction force motor 2a.

[Power assist control when the engine is stopped]
In the case where the driver steers after turning off the ignition switch 8, in the first embodiment, the example in which the SBW control is continued is shown, but in the second embodiment, the mechanical backup mechanism 9 is operated to steer with the handle 1. By mechanically connecting the tire 3, power assist control can be performed.

  When the ignition switch 8 is turned off, the engine is stopped and power generation by the alternator is also stopped. Since the steered motor 4a and the steering reaction force motor 2a are driven by a battery, battery power is consumed. In order to perform SBW control, it is necessary to supply current to each of the steering motor 4a and the steering reaction force motor 2a. However, in the case of power assist control, it can be realized only by the steering motor 4a. Battery power consumption can be reduced.

  In addition, when the battery assist voltage is lowered when the engine is stopped, the battery voltage is detected and the battery power consumption is reduced by gradually reducing the assist force of the power assist control. Can do.

Next, the effect will be described.
In the vehicle steering control device of the second embodiment, the effects listed below are obtained in addition to the effects (1) to (6) of the first embodiment.

  (7) A mechanical backup mechanism 9 that mechanically connects the steering wheel 1 and the steered tire 3 is provided, and when the power stop of the vehicle is determined, the mechanical backup mechanism 9 is connected, and the turning motor 4a is used. Power assist control means (step S8, step S9) for performing a power assist control for giving a steering additional torque to the driver's steering torque. Therefore, the steering motor 4a and the steering reaction force motor 2a are used after the engine is stopped. Compared with the first embodiment in which steer-by-wire control is performed, battery power consumption can be suppressed.

(Other examples)
The best mode for carrying out the present invention has been described based on the first and second embodiments. However, the specific configuration of the present invention is not limited to the first and second embodiments. Design changes and the like within the scope not departing from the gist are also included in the present invention.

  For example, in the embodiment, the example in which whether or not to stop the power source of the vehicle is determined by turning off the ignition switch is shown. However, even when the power source is a hybrid or an electric power, the battery is not in a power generation state. The determination may be made by using a similar stop switch or the like, or by receiving a state signal indicating that power generation is not possible from a power supply system monitoring function on the vehicle side.

  In the embodiment, an example of application to a steer-by-wire system in which a steering wheel and a steered wheel are mechanically separated has been shown, but the present invention is applied to a steering control system such as an electric power steering system and a variable gear ratio system. Can be applied.

It is a figure which shows the structure of the steer-by-wire (SBW) system of Example 1. FIG. 3 is a flowchart illustrating a flow of a steering control process executed by a steering reaction force controller 5 and a steering controller 6 according to the first embodiment. It is a figure which shows the conventional SBW system completion | finish determination method. It is a figure explaining the problem at the time of misrecognizing that the vehicle speed is zero during driving in the conventional SBW system end determination method. In the conventional SBW system end determination method, it is a figure explaining the problem at the time of misrecognizing that it is drive | working while a vehicle stops. It is a figure which shows the SBW system completion | finish determination effect | action of Example 1. FIG. It is a figure which shows the structure of the SBW system of Example 2. FIG. 6 is a flowchart illustrating a flow of a steering control process executed by a steering reaction force controller 5 and a steering controller 6 according to a second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering reaction force actuator 3 Steering tire 4 Steering actuator 5 Steering reaction force controller 6 Steering controller 7 Communication line 8 Ignition switch 9 Mechanical backup mechanism 10 Clutch

Claims (7)

Steering control means for driving and controlling at least one of steering means for adding steering torque to the steering wheel and steering reaction force means for adding steering force to the steering wheel;
Power stop determining means for determining whether or not the power source of the vehicle stops;
Tire input detection means for detecting input from the road surface to the tires of the vehicle;
A steering control stop means for stopping the steering control when it is determined that the power of the vehicle is stopped and the tire input does not change for a predetermined time;
A vehicle steering control device comprising: The vehicle steering control device according to claim 1,
Provided with hand release detecting means for detecting whether or not the driver has released his hand from the steering wheel;
The vehicle steering control device, wherein the steering control stop means stops the steering control when the released state continues for the predetermined time or more. The vehicle steering control device according to claim 2,
Steering torque detection means for detecting steering torque input to the steering wheel;
The vehicle release control means, wherein the release control means determines that the release state is a release state when the state where the steering torque does not change continues for the predetermined time. In the vehicle steering control device according to claim 3,
The steering reaction force means has a steering reaction force motor,
The vehicle steering control device, wherein the hand release detecting means detects the steering torque change based on a change in current flowing in the steering reaction force motor. The vehicle steering control device according to any one of claims 1 to 5,
The vehicle steering control device, wherein the tire input detection means detects the tire input change from a rack axial force change. The vehicle steering control device according to claim 5,
The steering control means has a steering motor,
The vehicle tire steering control device, wherein the tire input detection means detects a change in the rack axial force based on a change in current flowing in the steering motor. The vehicle steering control device according to any one of claims 1 to 6,
The handle and the steering wheel are mechanically separated from each other,
A backup mechanism for mechanically connecting the handle and the steering wheel;
Power assist control means for performing power assist control for connecting the backup mechanism and applying steering additional torque to the driver's steering torque using the steering motor when the power stop of the vehicle is determined;
A vehicle steering control device comprising:

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