JP5045138B2 - Steering control device - Google Patents

Description

  The present invention relates to a steering control device that performs steering control.

  Conventionally, when a phenomenon has occurred in which the vehicle flows in the left-right direction during straight running (hereinafter referred to as “deflection” or “vehicle flow”), electric power steering (EPS) is used. ), A technique for steering assist is proposed. For example, Patent Document 1 describes a technique for performing steering assist by moving an assist torque map defining a relationship between an input steering torque and an assist torque in the left-right direction when there is a road surface cant. Has been. Patent Document 2 describes a technology for prohibiting lane departure prevention control when the steering torque is equal to or greater than a predetermined value in a driving assistance device that performs lane departure prevention control. Furthermore, Patent Document 3 describes a technique related to the present invention.

JP 2003-267250 A JP-A-2005-343305 JP-A-11-334631

  However, in the technique described in Patent Document 1 described above, by moving the assist torque map in the left-right direction, the assist characteristic has a gradient when the steering torque is approximately 0, and the steering assist may not be stable. . Further, there is a relatively large difference in the steering torque to be input between the case of steering to the right and the case of steering to the left. Even with the techniques described in Patent Documents 2 and 3 described above, it is difficult to suppress the deflection of the vehicle without causing such a left-right difference in steering torque.

  The present invention has been made to solve the above-described problems, and a steering control device capable of effectively suppressing deflection generated in a vehicle while suppressing generation of a left-right difference in steering torque. The purpose is to provide.

In one aspect of the present invention, in the steering control device that generates assist torque with respect to the steering torque input by the driver, the steering torque input by the driver includes a predetermined point including an origin where the steering torque is zero. If within range, when running the steering assist in accordance with the first assist characteristic imparting assist torque deflection direction opposite the direction of the vehicle, said steering torque inputted by the driver is out of the predetermined range , the example Bei steering control means for performing steering assist in accordance with a second assist characteristic imparting assist torque corresponding to the steering torque, the first assist characteristic so that the assist characteristic asymmetrical to the origin And the range in the same direction as the deflection direction is set wider than the direction opposite to the deflection direction. The assist characteristic is set to be an assist characteristic that is symmetrical with respect to the origin, and the deflection direction is a state in which a phenomenon occurs in which the vehicle flows in the left direction or the right direction during straight running. , The direction in which the vehicle flows.

The steering control device is preferably used for generating assist torque with respect to the steering torque input by the driver. Specifically, the steering control device applies assist torque in the direction opposite to the vehicle deflection direction when the steering torque input by the driver is within a predetermined range including the origin where the steering torque is zero. Steering assist is performed in accordance with the first assist characteristic set to be performed. According to such a first assist characteristic, when a deflection occurs in the vehicle, a steering torque in the direction opposite to the deflection direction of the vehicle can be appropriately applied in a state where the steering torque is substantially zero. Therefore, according to the steering control device described above, it is possible to effectively suppress the deflection generated in the vehicle during the straight running while suppressing the occurrence of the left / right difference in the steering torque. Therefore, the driver can appropriately maintain the straight traveling state. The deflection direction means a direction in which the vehicle flows in a state where a phenomenon occurs in which the vehicle flows in the left direction or the right direction during straight running.
Specifically, the first assist characteristic is set so as to be asymmetrical with respect to the origin, and the range in the same direction as the deflection direction is set wider than the direction opposite to the deflection direction. Has been. Thereby, generation | occurrence | production of the left-right difference of a steering torque, etc. can be suppressed effectively.
On the other hand, when the steering torque input by the driver is out of the predetermined range, the steering control device executes steering assist according to the second assist characteristic that provides assist torque according to the steering torque. This second assist characteristic is set to be an assist characteristic that is symmetrical with respect to the origin.

  In another aspect of the steering control apparatus, the steering control means calculates an assist torque amount to be applied in the predetermined range based on at least the vehicle speed and the steering torque. Thereby, the level of the assist torque in the steering assist can be appropriately changed according to the vehicle speed, the steering torque, and the like.

  Preferably, the steering control device includes a deflection direction detection unit that detects a deflection direction in the vehicle, and the steering control unit is configured to perform the predetermined range based on the deflection direction detected by the deflection direction detection unit. The direction in which the assist torque is applied can be switched.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[overall structure]
First, the overall configuration of the steering control system 50 to which the steering control device according to the present embodiment is applied will be described. FIG. 1 is a schematic diagram showing the configuration of the steering control system 50.

  The steering control system 50 includes a steering wheel 1, a steering shaft 2, a rotation angle sensor 3, a motor 5, a steering torque sensor 6, a rack and pinion unit 7, tie rods 8r and 8l, and knuckle arms 9r and 9l. And wheels (front wheels) 10Fr, 10Fl, a vehicle speed sensor 12, and a controller 20. In the following, “r” and “l” attached to the end of the reference numerals of the tie rods 8r and 8l, the knuckle arms 9r and 9l, and the wheels 10Fr and 10Fl will be omitted if they are used without distinction. And Hereinafter, the steering wheel is also simply referred to as “steering”.

  The steering control system 50 is configured by a so-called electric power steering (EPS) system. Specifically, the steering control system 50 is mounted on a vehicle, performs drive control of a motor 5 that steers and drives a wheel 10 </ b> F that is a steered wheel, and steers the steered wheel according to an operation of the steering wheel 1. It is.

  The steering wheel 1 is operated by the driver to turn the vehicle. The steering wheel 1 is connected to the rack and pinion unit 7 via the steering shaft 2. The steering shaft 2 is provided with a rotation angle sensor 3, a motor 5, and a steering torque sensor 6.

  The motor 5 is constituted by a reduction gear, an electric motor, or the like, and is controlled by a control signal S5 supplied from the controller 20. The reaction force motor 5 generates assist torque (steering assist force) in response to steering by the driver and improves steering stability and steering feeling, for example, in order to improve steering feeling and steering stability. An additional damping force is generated.

  The rotation angle sensor 3 detects a rotation angle corresponding to the operation of the steering wheel 1 by the driver. The rotation angle sensor 3 supplies a detection signal S3 corresponding to the detected rotation angle to the controller 20. The steering torque sensor 6 detects steering torque (hereinafter also referred to as “input torque”) input by the driver. The steering torque sensor 6 supplies a detection signal S6 corresponding to the detected steering torque to the controller 20. Further, the vehicle speed sensor 12 detects the vehicle speed and supplies a detection signal S12 corresponding to the detected vehicle speed to the controller 20.

  The rack and pinion unit 7 is configured by a rack, a pinion, or the like, and operates by transmitting rotation from the steering shaft 2. Further, a tie rod 8 and a knuckle arm 9 are connected to the rack and pinion unit 7, and a wheel 10 </ b> F is connected to the knuckle arm 9. In this case, when the tie rod 8 and the knuckle arm 9 are operated by the rack and pinion unit 7, the wheel 10F connected to the knuckle arm 9 is steered.

  The controller 20 includes a CPU, a ROM, a RAM, an A / D converter, and the like (not shown). The controller 20 corresponds to an ECU (Electronic Control Unit) in the vehicle. The controller 20 controls the motor 5 mainly based on detection signals supplied from the various sensors described above. In the present embodiment, the controller 20 executes steering control for generating assist torque with respect to the steering torque input by the driver. Specifically, the controller 20 performs control to generate assist torque from the motor 5 based on at least the steering torque and the vehicle speed. In this case, the controller 20 supplies the control signal S5 to the motor 5 based on the detection signal S6 acquired from the steering torque sensor 6 and the detection signal S12 acquired from the vehicle speed sensor 12. As described above, the controller 20 corresponds to the steering control device in the present invention. Specifically, the controller 20 functions as steering control means in the present invention.

[Steering control method]
Next, the steering control method executed by the controller 20 will be specifically described.

  In the present embodiment, steering assist is executed in order to effectively suppress a phenomenon in which the vehicle flows in the left-right direction during straight running (hereinafter referred to as “deflection” or “vehicle flow”). To do. That is, the controller 20 performs control to generate assist torque from the motor 5 so that the driver can appropriately maintain the straight traveling state when the vehicle is deflected.

  Specifically, in the present embodiment, the controller 20 performs steering according to the assist characteristic set to apply assist torque in the direction opposite to the deflection direction of the vehicle in a predetermined range including the origin where the input torque is zero. Assist. Specifically, the controller 20 performs steering assist based on assist characteristics set asymmetrically with respect to the origin within a predetermined range. In addition, the controller 20 performs steering assist according to the assist characteristics set substantially symmetrically with respect to the origin where the input torque is 0 in a range other than the predetermined range. That is, in a range other than the predetermined range, steering assist is performed according to general assist characteristics.

  Note that the above-described vehicle deflection may be caused by a difference between the left and right sides of the vehicle, or may be caused by the road side. Specifically, deflection occurs when there is a left-right difference on the vehicle side, such as when the left-right difference in the conicity component of the wheels is large, or when the suspension characteristics (for example, camber angle) are different between the left and right. In addition, deflection occurs when the road surface has a large cant (camber angle).

  Here, with reference to FIG. 2, the steering assistance which concerns on this embodiment is demonstrated concretely.

  FIG. 2 shows the input torque (steering torque) on the horizontal axis and the assist torque on the vertical axis. In this case, the right direction on the horizontal axis indicates that the input torque is input in the left direction, and the left direction on the horizontal axis indicates that the input torque is input in the right direction. Further, the upward direction on the vertical axis indicates that assist torque is applied in the left direction, and the downward direction on the vertical axis indicates that assist torque is applied in the right direction.

  A broken line A1 indicates an assist torque map used when general steering assist is performed. The assist torque map A1 is set so that the assist torque is 0 in the region near the origin where the input torque is 0, and the assist torque according to the input torque is applied when the input torque becomes a certain level. . The assist torque map A1 has left-right symmetric assist characteristics in the left-right direction across the origin where the input torque is zero.

  A solid line A2 indicates an assist torque map used when performing steering assist according to the present embodiment. The assist torque map A2 is set so that uniform assist torque is applied to the left in a predetermined range B1 including the origin where the input torque is zero. Further, the assist torque map A2 has left-right asymmetric assist characteristics in the left-right direction across the origin in the predetermined range B1. Specifically, the predetermined range B1 is set so that the right range B2 is wider than the left range B3. Furthermore, the assist torque map A2 is set so that when the input torque exceeds the predetermined range B1, the assist torque on the assist torque map A1 is quickly changed from the uniform assist torque in the left direction described above. Thus, when the input torque exceeds the predetermined range B1, the assist torque map A2 is quickly shifted to the assist torque map A1, and the steering assist is performed according to the assist torque map A1 set to the left-right symmetric assist characteristics. Can do.

  Next, an operation when steering assist is performed according to the assist torque map A2 will be described. Here, consider a case where the vehicle travels on a road having a downward slope on the road surface (in this case, the vehicle tends to deflect rightward).

  According to the assist torque map A2, the left assist torque is applied in a state where the input torque is 0 (that is, a state where the steering 1 is released). Therefore, it is possible to suppress the vehicle from deflecting in the right direction, and the driver can appropriately maintain the straight traveling state. Even when the driver performs steering, when the input torque exceeds the predetermined range B1, the assist torque map A2 is quickly shifted to the assist torque map A1, and the steering assist is performed. It can be said that the difference (the difference in steering torque to be input between when steering in the right direction and when steering in the left direction) is small.

  Furthermore, according to the assist torque map A2, since the assist torque to be applied has a left-right difference (because the predetermined range B1 has an asymmetric assist characteristic with respect to the origin), the left-right difference in the steering torque is effectively reduced. can do. Specifically, in order to shift from the assist torque map A2 to the assist torque map A1 earlier in the left direction (that is, in the predetermined range B1, the left range B3 is set narrower than the right range B2). Therefore, when steering to the left, it is possible to appropriately prevent the assist torque from becoming excessive, in other words, the operation of the steering wheel 1 from becoming too light. In contrast, when the vehicle is steered in the right direction, the vehicle is originally deflected in the right direction due to the slope of the road surface. However, since the same assist torque as that in the left direction is added, the vehicle moves faster with respect to the steering torque. It tends to feel that the operation of the steering wheel 1 is light. In this case, according to the assist torque map A2, the assist torque map A2 shifts from the assist torque map A2 to the assist torque map A1 later in the right direction (that is, in the predetermined range B1, the right range B2 is changed to the left range B3). Therefore, it is possible to prevent the operation of the steering wheel 1 from being felt lightly.

  Here, when driving on a road having a downward slope on the road surface (in this case, the vehicle tends to deflect to the left), it is considered that the steering assist is performed according to the assist torque map A2. . In this case, since the left assist torque is applied near the input torque 0, the vehicle deflection is promoted, but it is considered that the driver tries to correct the steering by steering the steering 1 to the right. It is done. When the driver steers the steering 1 in this way, according to the assist torque map A2, the assist characteristic quickly shifts from the assist torque map A2 to the assist torque map A1, so that it is possible to appropriately suppress the deflection of the vehicle. I can say that.

  As described above, according to the steering control method according to the present embodiment, it is possible to effectively suppress the deflection generated in the vehicle during the straight running while suppressing the generation of the left / right difference in the steering torque. Therefore, the driver can appropriately maintain the straight traveling state.

  In the above description, the assist torque map A2 is set so as to apply the assist torque in the left direction in the predetermined range B1, but instead, the assist torque in the right direction is applied in the predetermined range B1. Alternatively, an assist torque map set in (1) may be used. In this case, the direction in which the assist torque is applied in the predetermined range B1 is preferably set according to the characteristics of the vehicle.

  Moreover, it is not limited to using the assist torque map in which the direction in which the assist torque is applied in the predetermined range B1 is fixed. In another example, the steering control system may be configured so that the direction in which the assist torque is applied can be changed by a switch or the like, and the direction in which the assist torque is applied may be changed by the driver operating the switch. That is, in this example, a driver operates a switch between an assist torque map set to apply assist torque in the left direction and an assist torque map set to apply assist torque in the right direction. Can be switched. For example, when the driver feels a rightward deflection, the switch can be operated so that a leftward assist torque is applied in the predetermined range B1, and the driver feels a leftward deflection. The switch can be operated so that assist torque in the right direction is applied in the predetermined range B1.

  Furthermore, in another example, the direction in which the assist torque is applied in the predetermined range B1 may be switched based on the detected deflection direction by detecting the deflection direction in the vehicle. That is, the direction in which the assist torque is applied may be automatically switched based on the deflection generated in the vehicle. In this case, when there is no deflection in the vehicle, a general assist torque map (that is, an assist torque map that does not apply assist torque in the predetermined range B1 or the like) can be used. The deflection generated in the vehicle can be obtained based on, for example, changes in the acceleration, yaw, steering torque, and the like in the vehicle detected by a sensor or the like.

[Assist torque calculation method]
Next, a method of calculating the assist torque amount (assist torque amount applied in the predetermined range B1) applied when using the assist torque map A2 described above will be described. In the present embodiment, the controller 20 calculates such an assist torque amount based on at least the vehicle speed and the steering torque. That is, the controller 20 performs a process of changing an assist torque amount (hereinafter, also referred to as “basic assist amount after vehicle deflection countermeasures”) for taking measures against vehicle deflection in accordance with vehicle speed, steering torque, and the like.

  FIG. 3 is a flowchart showing a basic assist amount calculation process after vehicle deflection countermeasures. This process is repeatedly executed by the controller 20 at a predetermined cycle.

  First, in step S101, the controller 20 acquires the vehicle speed. Specifically, the controller 20 acquires the detection signal S12 from the vehicle speed sensor 12. Then, the process proceeds to step S102.

  In step S102, the controller 20 calculates a vehicle speed gain based on the vehicle speed acquired in step S101. In this case, the controller 20 obtains the vehicle speed gain with reference to a vehicle speed gain map (stored in a memory or the like) that defines the relationship between the vehicle speed and the vehicle speed gain. According to the vehicle speed gain map, a substantially zero vehicle speed gain is obtained when the vehicle speed is relatively low, and a substantially constant vehicle speed gain is obtained when the vehicle speed exceeds a predetermined value. When the process in step S102 is completed, the process proceeds to step S106.

  In step S103, the controller 20 acquires a steering torque. Specifically, the controller 20 acquires the detection signal S6 from the steering torque sensor 6. Then, the process proceeds to step S104.

  In step S104, the controller 20 obtains the phase-compensated torque by removing noise in the steering torque acquired in step S103. Then, the process proceeds to step S105.

  In step S105, the controller 20 obtains a target correction amount based on the phase-compensated torque acquired in step S104. In this case, the controller 20 obtains the target correction amount with reference to a target correction amount map (stored in a memory or the like) that defines the relationship between the phase compensated torque and the target correction amount. According to the target correction amount map, a target correction amount having a predetermined value can be obtained in a region where the absolute value of the phase-compensated torque is relatively small. When the process of step S105 is completed, the process proceeds to step S106. Basically, the processes in steps S101 and S102 and the processes in steps S103 to S104 are performed in parallel.

  In step S106, the controller 20 calculates the vehicle deflection countermeasure control amount by multiplying the vehicle speed gain obtained in step S102 by the target correction amount obtained in step S105. Then, the process proceeds to step S108.

  In step S107, the controller 20 acquires a basic assist amount that is a basis for performing the steering assist. Specifically, the controller 20 refers to a map in which the vehicle speed and the basic assist amount are associated with each other, and acquires the basic assist amount corresponding to the current vehicle speed. Then, the process proceeds to step S108. Basically, the process of step S108 is performed in parallel with the processes of steps S101 to S106 described above.

  In step S108, the controller 20 adds the vehicle deflection countermeasure control amount obtained in step S106 and the basic assist amount obtained in step S107 to calculate the vehicle deflection countermeasure basic assist amount. Then, the controller 20 executes steering assist based on the calculated basic assist amount after countermeasures against vehicle deflection.

  FIG. 4 is a diagram illustrating an example of the basic assist amount after countermeasures against vehicle deflection obtained by the above-described processing. FIG. 4 shows the input torque on the horizontal axis and the assist torque on the vertical axis. Note that the input torque shown on the horizontal axis corresponds to the post-phase compensation torque after noise removal (torque obtained in step S104). A broken line C1 indicates an assist torque map (corresponding to the assist torque map A1 described above) before taking measures against vehicle deflection. A solid line C2 is an assist torque map after countermeasures against vehicle deflection (corresponding to the assist torque map A2 described above), and corresponds to the basic assist amount after countermeasures against vehicle deflection obtained by the above-described processing.

  In this case, by performing the processing shown in FIG. 3, the level of assist torque for taking countermeasures against deflection is appropriately set according to the vehicle speed, steering torque, etc., as shown by the white arrow C3 in FIG. Can be changed. Therefore, it is possible to more effectively suppress the deflection that occurs in the vehicle during straight running.

  In the above description, the example in which the assist torque amount (basic assist amount after countermeasures against vehicle deflection) is changed based on the vehicle speed or the like has been described. However, the present invention is not limited to this. In another example, the steering control system can be configured such that the assist torque amount can be changed by a switch or the like, and the assist torque amount can be changed by the driver operating the switch.

It is the schematic which shows the structure of the steering control system which concerns on this embodiment. It is a figure for demonstrating the assist torque map which concerns on this embodiment. It is a flowchart which shows the calculation process of the basic assist amount after a vehicle deflection countermeasure. It is a figure which shows an example of the basic assist amount after a vehicle deflection countermeasure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Rotation angle sensor 5 Motor 6 Steering torque sensor 7 Rack and pinion part 10F Wheel (front wheel)
12 Vehicle speed sensor 20 Controller 50 Steering control system

Claims (3)

In a steering control device that generates an assist torque with respect to a steering torque input by a driver,
When the steering torque input by the driver is within a predetermined range including the origin where the steering torque is 0, steering assist is performed according to a first assist characteristic that applies assist torque in a direction opposite to the deflection direction of the vehicle. run, when said steering torque inputted by the driver is out of the predetermined range, Bei give a steering control means for performing steering assist in accordance with a second assist characteristic that applies assist torque corresponding to the steering torque ,
The first assist characteristic is set to be an asymmetrical assist characteristic with respect to the origin, and the range in the same direction as the deflection direction is set wider than the direction opposite to the deflection direction. ,
The second assist characteristic is set to be a symmetrical assist characteristic with respect to the origin,
The steering control device according to claim 1, wherein the deflection direction is a direction in which the vehicle flows in a state in which a phenomenon occurs in which the vehicle flows in the left direction or the right direction during straight running .   The steering control device according to claim 1, wherein the steering control means calculates an assist torque amount to be applied in the predetermined range based on at least a vehicle speed and the steering torque. Comprising a deflection direction detecting means for detecting a deflection direction in the vehicle;
The steering control according to claim 1 or 2 , wherein the steering control means switches a direction in which the assist torque is applied in the predetermined range based on the deflection direction detected by the deflection direction detection means. apparatus.

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