JP5776969B2 - Steering control device - Google Patents

Description

  The present invention relates to a steering control device that applies a braking torque to a steering wheel.

  When a large steering force is required due to friction between a tire and a road surface, the electric power steering device applies assist torque for assisting the driver's steering operation by the motor.

JP 2009-179096 A

  When the steering wheel and the steering wheel are connected via the steering mechanism, the external force that the tire of the steering wheel receives from the road surface while the vehicle is traveling is transmitted to the steering wheel via the steering mechanism. For example, when the driver keeps the steering wheel in the neutral position while the vehicle is traveling straight ahead, when an external force that rotates the steering angle is input to the tire from the road surface, the rotational force is transmitted to the steering hole, and the steering wheel Is driven to rotate. For this reason, when the external force input to the tire increases and the amount of rotation of the steering wheel driven increases, there is a possibility that the driver may feel uneasy. In addition, if external force is frequently input to the tire, the driver must perform corrective steering frequently, which may impair running stability.

  Therefore, an object of the present invention is to provide a steering control device capable of improving the running stability of a vehicle.

In order to achieve the above object, the present invention provides a steering control device for a vehicle in which a steering wheel and a steered wheel are coupled via a steering mechanism, and the steered wheel is steered at a rudder angle according to the rotation of the steering wheel. A torque generating means, a first detecting means, a second detecting means, a lead phase determining means, an operation state determining means, and a control means.

The torque generating means applies torque to the steering wheel. The first detection means detects a steering angle generated on the steering wheel side as a steering angle. The second detection means detects the steering angle generated on the steered wheel side as an actual steering angle. The advance phase determination means determines whether or not the actual steering angle detected by the second detection means is an advance phase state in which the steering angle detected by the first detection means changes in one rotational direction in advance. To do. The operation state determination unit determines whether or not the steering wheel is in a non-operation state in which the steering operation is not performed. When the operation state determination unit determines that the control unit is in the non-operation state and the advance phase determination unit determines that the actual steering angle is in the advanced phase state, the control unit performs braking in a direction opposite to the one rotation direction. Torque is generated in the torque generation means, and when the operation state determination means determines that it is not in the non-operation state, no braking torque is generated in the torque generation means .

  In the above configuration, an external force for rotating the wheel steering angle is input from the road surface to the tire of the steering wheel while the vehicle is running, and the actual steering angle generated on the steering wheel side becomes the steering angle generated on the steering wheel side. On the other hand, when it changes in advance in one rotation direction, the advance phase determination means determines that the advance phase state is present, and the control means applies braking torque in the opposite direction to the one rotation direction to the torque generation means. generate. Since the braking torque generated by the torque generating means acts as a reaction force against the driven rotation of the steering wheel due to the external force from the road surface, the driven rotation of the steering wheel due to the external force (disturbance) from the road surface is suppressed. Therefore, the state of the steering wheel is stabilized, and the running stability of the vehicle is improved.

In addition , while the driver is performing the steering operation, no braking torque is generated, and the driver is not performing the steering operation, for example, when the vehicle is traveling straight ahead while holding the steering wheel in the neutral position, In addition, braking torque is generated when the actual steering angle advances and enters a phase state. Therefore, the state of the steering wheel during straight traveling is stabilized without impairing the operability when the steering wheel is actively operated, and the running stability of the vehicle is improved.

  The control means may generate a stronger braking torque as the phase difference between the steering angle and the actual steering angle is larger.

  In the above configuration, the stronger the external force input to the tires of the steered wheels, the greater the phase difference between the steering angle and the actual rudder angle, and the greater the braking torque that is generated, so the driven rotation of the steering wheel due to the external force from the road surface is reduced. It can be accurately suppressed.

  According to the present invention, the running stability of a vehicle can be improved.

It is a principal part schematic diagram of the vehicle provided with the steering control apparatus of one Embodiment of this invention. FIG. 2 is a functional configuration diagram of the steering control device of FIG. 1. It is a figure which shows the relationship between the steering angle in a stationary state, and an actual steering angle. It is a figure which shows the relationship between the steering angle in a steering state, and an actual steering angle, (a) shows the time of left steering, (b) shows the time of right steering, respectively. It is a figure which shows the relationship between the steering angle in this disturbance input state, and an actual steering angle, (a) shows the time of the external force input to the left direction, (b) shows the time of the external force input to the right direction, respectively. . It is a flowchart which shows the braking torque generation process which the steering control apparatus of FIG. 1 performs.

  Hereinafter, an embodiment in which a steering control device of the present invention is applied to a power steering device 1 will be described with reference to the drawings.

  As shown in FIGS. 1 and 2, left and right front wheels (steering wheels) WL and WR of the vehicle are connected to both ends of the rack shaft 12 via tie rods 11, respectively. The rack shaft 12 is connected to a lower end portion of a steering shaft 13 via a pinion (not shown), and a steering hole 14 is fixed to the upper end portion of the steering shaft 13. When the steering wheel 14 is set to the neutral position, both the left and right front wheels WL, WR are in a straight traveling state along the front-rear direction, and when the steering wheel 14 is rotated (steered) from the neutral position to the left-right direction, the steering shaft 13, the left and right front wheels WL and WR are steered through the pinion, the rack shaft 12 and the tie rod 11. That is, the steering shaft 13, the pinion, the rack shaft 12, and the tie rod 11 constitute the steering mechanism 2 that connects the steering wheel 14 and the left and right front wheels WL, WR, and the left and right at a steering angle θ corresponding to the rotation of the steering wheel 14. The front wheels WL and WR are steered.

  Since the steering mechanism 2 has torsional rigidity, the steering angle θ generated by the steering mechanism 2 is larger on the input side of the rotational force than on the output side. For example, when the steering wheel 14 is steered, the steering angle θ generated on the steering wheel 14 side is larger than the steering angle θ generated on the front wheels WL, WR side. On the contrary, when an external force for rotating the front wheels WL and WR is input to the tires 15 of the front wheels WL and WR from the road surface while the vehicle is running, the steering angle θ generated on the front wheels WL and WR side is steered. It becomes larger than the steering angle θ generated on the wheel 14 side. In the following, the steering angle θ when the vehicle travels straight while the steering wheel 5 is in the neutral position is 0 ° (reference), and the time when the steering wheel 5 rotates rightward (clockwise) from the neutral position is positive, The description will be made assuming that the rotation to the left (counterclockwise) is negative.

  A steering angle sensor 6 composed of a rotary encoder or the like is provided on the upper end side (steering wheel 14 side) of the steering shaft 13. The steering angle sensor 6 functions as first detection means for sequentially detecting the steering angle θ generated on the steering wheel 14 side as the steering angle θa, and outputs the detected value to the controller 4 described later as a steering angle signal.

  Further, the steering shaft 13 is provided with a torsion bar (not shown) that twists according to the steering torque input to the steering wheel 14, and the torque sensor 5 sequentially detects the torsion amount and direction of the torsion bar. . The detection value of the torque sensor 5 (a torsion bar twist amount and direction) is output to the controller 4 as a torque signal.

  The power steering device 1 is a rack coaxial type electric power steering device having a ball screw type conversion mechanism that converts rotational torque of a motor (torque generating means) 3 into force in the reciprocating direction of the rack shaft 12. A ball screw groove (not shown) is formed on a part of the outer peripheral surface of the rack shaft 12, and a ball screw groove corresponding to the ball screw groove is formed in the rotor of the motor 3 arranged coaxially with the rack shaft 12. The ball nut which has on a peripheral surface is being fixed. A plurality of balls are accommodated between the pair of ball screw grooves, and the rotational motion of the motor 3 is converted into the reciprocating motion of the rack shaft 12 by the ball screw. The motor 3 is vector-controlled by a command signal from the controller 4 and is appropriately rotated in both forward and reverse directions. In the vector control, a vector serving as a power running is instructed when an assist torque for assisting a driver's steering operation is generated, and a vector serving as a regeneration is instructed when a braking torque for suppressing the rotation of the steering wheel 14 is generated. When the motor 3 is driven, the rack shaft 12 is driven in the axial direction (right or left in the vehicle width direction), and torque (assist torque or braking torque) is applied to the steering hole 14.

  The motor 3 is provided with a magnetic position sensor 7 that detects the rotational position of the motor 3. The detected value of the magnetic position sensor 7 varies according to the movement of the rack shaft 12, and the steering angle θ changes according to the movement of the rack shaft 12. Accordingly, the magnetic position sensor 7 functions as second detection means for sequentially detecting the steering angle θ generated on the front wheels WL, WR side as the actual steering angle θb, and outputs the detected value to the controller 4 as an actual steering angle signal. . Instead of the magnetic position sensor 7, a sensor that directly detects the position of the rack shaft 12 may be provided as the second detection means.

  The controller 4 includes a CPU (Central Processing Unit) 8 and a storage unit (not shown). The storage unit is configured by a recording medium such as a RAM (Random Access Memory) and a ROM (Read Only Memory), for example, and stores various programs and various data for the CPU 8 to execute various processes. The various programs include a motor control processing execution program for the CPU 8 to execute motor control processing (assist torque generation processing and braking torque generation processing). Further, the storage unit has a storage area in which various detection values and information are stored in a readable and writable manner.

  The CPU 8 functions as a steering assist control unit 16, a motor vector control unit (control unit) 17, and a phase detection unit (phase determination unit, operation state determination unit) 18 by executing an assist torque generation process and a braking torque generation process. To do.

  In the assist torque generation process, the steering assist control unit 16 determines the driver for the steering wheel 14 based on the detection value (the magnitude and direction of the steering input torque corresponding to the detection value) indicated by the torque signal input from the torque sensor 5. The direction and magnitude of the assist torque that assists the steering is determined. The motor vector control unit 17 outputs a command signal for generating the assist torque determined by the steering assist control unit 16 to the motor 3. A vehicle speed sensor, a yaw rate sensor, and the like may be provided, and the magnitude of the assist torque may be determined based on other information such as the vehicle speed, acceleration, and yaw rate and the steering input torque.

  In the braking torque generation process, the phase detector 18 determines whether or not the steering wheel 14 is in a non-operating state in which the steering operation is not performed. The steering speed (rotational angular speed) of the steering wheel 14 is calculated as a time change (time differential value) of the steering angle θa detected by the steering angle sensor 6, and when the calculated steering speed is less than or equal to a predetermined value, Judge that there is. The method for determining whether or not the vehicle is in the non-operating state is not limited to the above. For example, the steering acceleration (rotational angular acceleration) of the steering wheel 14 is calculated, and the non-operating state is calculated when the calculated steering acceleration is equal to or less than a predetermined value. It may be determined that the detected value indicated by the torque signal from the torque sensor 5 is in a non-operating state when the time change (time differential value) is equal to or less than a predetermined value.

  The phase detector 18 also detects the phase of the steering angle θa detected by the steering angle sensor 6 (angle from the neutral position) and the phase of the actual steering angle θb detected by the magnetic position sensor 7 (angle from the neutral position). Are sequentially compared, and it is determined whether or not the actual steering angle θb is an advanced phase state in which the steering angle θb changes in advance in one rotational direction with respect to the steering angle θa. The detected value indicated by the actual steering angle signal from the magnetic position sensor 7 is a displacement in the linear direction of the rack shaft 12 and is a value indirectly indicating the steering angle θ. For this reason, the detected value (axial displacement) indicated by the actual steering angle signal is converted into an angle corresponding to the steering angle θ and compared with the steering angle θa.

  In determining whether or not the vehicle is in the advanced phase state, every time the steering angle θa and the actual steering angle θb are acquired, the absolute value (phase difference) of the difference between the steering angle θa and the actual steering angle θb is a predetermined value or more. It is determined whether or not there is. Further, the time change (time differential value) of the steering angle θa and the actual steering angle θb is calculated, and the calculated values are stored in time series. When the phase difference is equal to or greater than a predetermined value, it is determined whether or not the vehicle is in the advanced phase state based on the temporal change of the steering angle θa and the actual steering angle θb stored in time series. Specifically, the steering angle θa and the actual steering angle θb change in the same rotational direction, the time change of the actual steering angle θb is larger than the time change of the steering angle θa, and the time change of the phase difference (steering) If the difference between the time change of the angle θa and the time change of the actual steering angle θb is increased, it is determined that the lead phase state is reached. Note that the method of determining the lead phase state is not limited to the above, and for example, the determination of whether or not the phase difference is a predetermined value or more may be omitted. Further, it is determined from the steering angle θa or the actual steering angle θb whether or not the vehicle is in the straight traveling state, and when the vehicle is in the straight traveling state, the displacement (phase) of the steering angle θa with respect to the neutral position and the actual steering angle θb The displacement (phase) may be compared, and if the actual steering angle θb is displaced larger than the steering angle θa, it may be determined that the leading phase state is present.

  Further, when the phase detector 18 determines that the state is the leading phase state, the magnitude of the braking torque (braking torque instruction value) generated by the motor 3 is determined according to the phase difference between the steering angle θa and the actual steering angle θb. Then, a braking instruction signal indicating the determined braking torque instruction value is output to the motor vector control unit 17. The direction of the braking torque is a direction toward the opposite direction to the advance phase direction of the actual steering angle θb. For example, when the actual steering angle θb precedes the steering angle θa in the right rotation direction, braking torque in the left rotation direction is generated. In the present embodiment, a positive braking torque value is set when generating braking torque in the right rotation direction, and a negative braking torque value is set when generating braking torque in the left rotation direction. . Further, the braking torque instruction value is determined so that a stronger braking torque is generated as the phase difference is larger. In this embodiment, the braking torque instruction value is determined so that the absolute value of the braking torque instruction value increases in proportion to the phase difference. Further, a predetermined arithmetic expression is stored in advance as a correspondence relationship between the phase difference and the braking torque instruction value, and the braking torque instruction value is calculated using the phase difference. The correspondence relationship between the phase difference and the braking torque command value is not limited to a proportional relationship as long as the braking torque command value increases as the phase difference increases, and may be set as a map or a table. Good.

  The motor vector control unit 17 outputs a command signal for generating a braking torque having a strength corresponding to the start instruction signal input from the phase detection unit 18 to the motor 3. That is, the motor vector control unit 17 responds to the phase difference between the steering angle θa and the actual steering angle θb when the phase detector 18 determines that the actual steering angle θb is in the non-operating state and is in the advanced phase state. A braking torque is generated in the motor 3.

  Here, the relationship between the steering angle θa that is the steering angle θ generated on the steering wheel 14 side and the actual steering angle θb that is the steering angle θ generated on the front wheels WL and WR side will be described with reference to FIGS. I will explain.

  In a state where the steering wheel 14 is set to the neutral position and both the left and right front wheels WL and WR are traveling straight in the front-rear direction, both the steering angle θa and the actual steering angle θb are theoretically 0 ° as shown in FIG. (Θa = θb = 0 °), and both coincide.

  When the steering wheel 14 is steered from the straight traveling state, the absolute value of the steering angle θa becomes larger than the absolute value of the actual steering angle θb as shown in FIG. 4 due to the torsional rigidity of the steering mechanism 2 ( │θa│> │θb│). That is, the steering angle θa is a leading phase with respect to the actual steering angle θb.

  On the other hand, when an external force for rotating the front wheels WL and WR is input to the tires 15 of the front wheels WL and WR from the road surface in a straight traveling state, as shown in FIG. The absolute value is larger than the absolute value of the steering angle θa (| θb |> | θa |). That is, the actual steering angle θb is a leading phase with respect to the steering angle θa. In this embodiment, in such a case, a braking torque is generated to suppress the fluctuation of the steering hole 14 due to a disturbance from the road surface.

  Next, the braking torque generation process executed by the CPU 8 will be described with reference to FIG. This process is repeatedly executed every predetermined time when the ignition key of the vehicle is in the ON state.

  When this process is started, the phase detection unit 18 calculates the steering speed of the steering wheel 14 as a time change of the steering angle θa, and determines whether or not the calculated steering speed is equal to or less than a predetermined value (step S1). ).

  When the steering speed is equal to or lower than the predetermined value (step S1: YES), the phase detector 18 detects the phase of the steering angle θa and the phase of the actual steering angle θb (step S2), and the actual steering angle θb becomes the steering angle θa. On the other hand, it is determined whether or not the lead phase state changes in advance in one rotation direction (step S3).

  When the actual steering angle θb is in the advanced phase state (step S3: YES), the phase detector 18 calculates a braking torque instruction value proportional to the phase difference between the steering angle θa and the actual steering angle θb (step S4). . The motor vector control unit 17 outputs a command signal for generating the braking torque of the braking torque instruction value calculated by the phase detection unit 18 to the motor 3 (step S5), and ends this process.

  On the other hand, when the steering speed of the steering wheel 14 exceeds the predetermined value (step S1: NO) and when the actual steering angle θb is not in the advanced phase state (step S3: NO), the braking torque is not generated. This process is terminated.

  Thus, according to the present embodiment, an external force (disturbance) that tries to rotate the wheel steering angles (tire angles) of the front wheels WL and WR is applied from the road surface to the tires 15 of the front wheels WL and WR while the vehicle is traveling. When the actual steering angle θb generated on the front wheels WL, WR side is changed in advance in one rotation direction with respect to the steering angle θa generated on the steering wheel 14 side, it is determined that the lead phase state is established, A braking torque is applied to the steering hole 14 in the direction opposite to the one rotation direction. Since this braking torque acts as a reaction force against the driven rotation of the steering wheel 14 due to the external force from the road surface, the driven rotation of the steering wheel 14 due to the external force from the road surface is suppressed. Therefore, the state of the steering wheel 14 is stabilized, and the running stability of the vehicle is improved.

  In addition, no braking torque is generated while the driver is performing the steering operation, and the driver is not performing the steering operation, for example, when the vehicle that holds the steering wheel 14 in the neutral position is traveling straight ahead. In addition, braking torque is generated when the actual steering angle θb advances and enters a phase state. Therefore, it is possible to stabilize the state of the steering wheel 14 when traveling straight and improve the running stability of the vehicle without impairing the operability when the steering wheel 14 is actively operated.

  Further, the stronger the external force input to the tires 15 of the front wheels WL and WR (the greater the disturbance), the greater the phase difference between the steering angle θa and the actual steering angle θb, and the generated braking torque becomes stronger. The driven rotation of the steering wheel 14 due to the external force can be accurately suppressed.

  In addition, the said embodiment is an example of this invention and can be changed in the range which does not deviate from this invention.

  For example, a constant braking torque may be generated regardless of the phase difference between the braking / steering angle θa and the actual steering angle θb. The detection positions of the braking / steering angle θa and the actual steering angle θb are not limited to the above, and the detection method is not limited to the above.

  The present invention is widely applicable to vehicles in which a steering wheel and a steering wheel are connected via a steering mechanism.

1: Power steering device (steering control device)
2: Steering mechanism 3: Motor (torque generating means)
4: Controller 5: Torque sensor 6: Steering angle sensor (first detection means)
7: Magnetic position sensor (second detection means)
8: CPU
12: Rack shaft 13: Steering shaft 14: Steering wheel 15: Tire 16: Steering assist control unit 17: Motor vector control unit (control means)
18: Phase detection unit (phase determination means, operation state determination means)
WL, WR: Front wheels (steering wheels)
θ: rudder angle θa: steering angle θb: actual rudder angle

Claims (2)

A steering control device for a vehicle in which a steering wheel and a steering wheel are connected via a steering mechanism, and the steering wheel steers at a steering angle corresponding to the rotation of the steering wheel,
Torque generating means for applying torque to the steering wheel;
First detection means for detecting a steering angle generated on the steering wheel side as a steering angle;
Second detection means for detecting a steering angle generated on the side of the steering wheel as an actual steering angle;
Advance phase determination for determining whether or not the actual steering angle detected by the second detection means is an advance phase state in which the steering angle detected by the first detection means is changed in advance in one rotational direction. Means,
An operation state determination means for determining whether or not the steering wheel is in a non-operation state in which the steering operation is not performed;
When the operation state determination means determines that the non-operation state is present, and the advance phase determination means determines that the actual steering angle is an advance phase state, the direction is opposite to the one rotation direction. Control means for causing the torque generating means to generate a braking torque and not causing the torque generating means to generate the braking torque when the operating state determining means determines that it is not in the non-operating state. Steering control device. The steering control device according to claim 1,
The steering control device, wherein the control means generates a stronger braking torque as the phase difference between the steering angle and the actual steering angle is larger .

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