JP4586517B2 - Steering control device - Google Patents

Description

  The present invention relates to a steering control device, and more particularly to a steering control device that suppresses vibration transmitted from a steering wheel to a driver.

  The power steering device generates an assist force using an electric motor or the like. The power steering device assists the steering force applied by the driver to the steering wheel, and reduces the force for the driver to apply the steering force.

By the way, when the vehicle travels, vibrations such as brake vibration and flutter during driving of the vehicle are transmitted to the driver through the steering wheel and sometimes become unpleasant vibration. Thus, conventionally, some vehicles equipped with a power steering device use a steering device to suppress vibration transmitted to the steering wheel. As an example, there is a power steering device disclosed in Japanese Patent Laid-Open No. 6-127406. This power steering apparatus has means for applying an assist force to a steering shaft connected to a steering wheel. And the higher the detected vibration level is, the more the vibration is suppressed by increasing the assisting force on the steering shaft.
JP-A-6-127406

  However, in the power steering device disclosed in Patent Document 1, vibration is suppressed by simply increasing the assist force. For this reason, although the effect of suppressing the vibration is exhibited by controlling the assist force in the power steering device, there is a problem that the steering feeling may be deteriorated depending on the traveling state of the vehicle.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a steering control device that can suitably suppress vibration transmitted to a steering wheel and prevent deterioration of steering feeling for a driver.

A steering control device according to the present invention that has solved the above-described problems is a steering control device that performs steering control of a running vehicle, and determines a traveling state of the vehicle, a frequency detection means that detects a vibration frequency of a steering system of the vehicle A driving state determining means, a motor for applying an assisting force to the steering system of the vehicle, and an assisting force controlling means for controlling the assisting force of the motor. The assisting force controlling means has a predetermined vibration frequency by the frequency detecting means. together it is detected, when it the vehicle is running straight is determined by the traveling state determining means reduces the assist force of the motor, the damping force of the motor is shall be maintained normal state.

  When suppressing vibration for the driver, it is conceivable to increase the damping ratio ζ in the steering system. The damping ratio ζ indicates the degree of convergence of vibration and is given by the following equation (1).

ζ = C / 2 (IK) ^1/2 (1)

Where I: Steering system moment of inertia
C: Damping force of motor
K: Rigidity (constant)

  As can be seen from the above equation (1), in order to increase the damping ratio ζ, the steering system inertia moment (hereinafter referred to as “assist force”) I may be decreased, or the damping force C may be increased. Here, if the damping force C of the motor is increased when the traveling state of the vehicle is a straight traveling state, the feeling of viscosity is increased, and the clarity of the steering wheel being in the neutral position is reduced, and the steering feeling is deteriorated. May be incurred.

  Therefore, in the steering control device according to the present invention, when the vibration frequency is a predetermined frequency and the traveling state of the vehicle is a straight traveling state, the assist force I is decreased to increase the damping ratio ζ. . By performing such control, the damping ratio ζ increases, so that vibration transmitted to the steering wheel can be suppressed. Further, since the damping ratio ζ can be increased without increasing the damping force C, it is possible to maintain the clarity of the neutral position in the straight traveling state, thereby preventing the steering feeling from being deteriorated.

  Further, a steering control device according to the present invention that has solved the above-described problems is a steering control device that performs steering control of a running vehicle. Frequency detection means that detects a vibration frequency of a steering system of the vehicle, and a traveling state of the vehicle. A traveling state determining means for determining, a motor for applying an assist force to the steering system of the vehicle, and a damping force control means for controlling the damping force of the motor. When the frequency is detected and the traveling state determining means determines that the vehicle is turning, the damping force of the motor is increased.

  In order to suppress vibration transmitted to the steering wheel by reducing the damping ratio ζ as in the above case, it is considered that the assist force I is reduced when the vehicle is in a turning state instead of a straight traveling state. . In this case, the force for turning the steering wheel is required for turning, and the assist force I is reduced. Therefore, a large force is required when the driver turns the steering wheel, which may lead to deterioration of the steering feeling. There is.

  Therefore, in the steering control device according to the present invention, when the vibration frequency is a predetermined frequency and the traveling state of the vehicle is in a turning state, the damping force C of the motor is increased to increase the damping ratio ζ. I do. By performing such control, the damping ratio ζ increases, so that vibration transmitted to the steering wheel can be suppressed. Further, since the damping ratio ζ can be increased without reducing the assist force I, it is possible to avoid a decrease in the assist force in the turning state, and thus it is possible to prevent the steering feeling from being deteriorated.

  The assist force control means further controls the assist force of the motor, and the assist force control means detects the predetermined vibration frequency by the frequency detection means, and the vehicle is in a straight traveling state by the progress state determination means. It is also preferable to reduce the assist force of the motor when it is determined. As a result, the damping ratio ζ can be increased both when the vehicle is traveling straight and when the vehicle is turning, so that vibration can be suppressed without deteriorating the steering feeling.

  It is also preferable to include a frictional force applying unit that applies a physical frictional force to the steering system when a predetermined vibration frequency is detected by the frequency detecting unit. Thereby, vibration can be more reliably suppressed by using a physical frictional force in order to suppress vibration.

  According to the steering control device according to the present invention, it is possible to suitably suppress vibration transmitted to the steering wheel and to prevent deterioration of the steering feeling for the driver.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components in the drawings are denoted by the same reference numerals as much as possible, and redundant descriptions may be omitted.

  A steering control apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram of a vehicle including a steering control device according to the present embodiment, and FIG. 2 is a block configuration diagram of the steering control device.

  The vehicle 1 includes a steering wheel 2. One end of a steering shaft 3 is connected to the steering wheel 2, and a pinion gear 4 in a rack and pinion mechanism is provided at the other end of the steering shaft 3. A rack shaft 5 of a rack and pinion mechanism is disposed on the other end side of the steering shaft 3, and the rack and pinion mechanism is configured by meshing the pinion gear 4 and the rack shaft 5.

  Further, steered wheels 7 are attached to both ends of the rack shaft 5 via tie rods 6 respectively. These steering wheel 2, steering shaft 3, rack and pinion mechanism, etc. constitute a steering system. When the driver rotates the steering wheel 2, the rotation of the steering wheel 2 is transmitted to the steered wheel 7 attached to the tip of the rack shaft 5 via the steering shaft 3 and the rack and pinion mechanism. Turn left or right.

  The vehicle 1 is provided with a steering control device 10. The steering control device 10 includes an ECU (electronic control device) 11, an electric motor 12, and a friction force applying unit 13 that is a friction force applying means of the present invention.

  The ECU 11 is an electronic control device that controls the electric motor 12 and the frictional force applying unit 13, and is configured mainly by a computer including a CPU, a ROM, and a RAM, for example. As shown in FIG. 2, the ECU 11 includes a control start determination unit 21, a progress state determination unit 22, an assist force control unit 23, a damping force control unit 24, and a friction force application control unit 25. In addition, a steering angle sensor 14 and a torque sensor 15 are electrically connected to the ECU 11.

  The electric motor 12 is a motor that applies assist force to the steering system of the vehicle 1. The assisting force generated by the electric motor 12 can assist the steering force applied to the steering wheel 2 by the driver.

  The frictional force applying unit 13 constrains the rotation of the steering shaft 3 by applying a physical frictional force to the steering shaft 3. An example of the frictional force applying unit 13 includes a mechanism that applies a frictional force by pressing a pad against the steering shaft 3.

  The steering angle sensor 14 is attached to the steering shaft 3, for example, and detects the steering angle of the steering wheel 2. The steering angle sensor 14 outputs the detected steering angle to the control start determination unit 21 in the ECU 11.

  The torque sensor 15 is attached to the steering shaft 3, for example, and detects the torque when the steering shaft 3 rotates by the steering force transmitted from the steering wheel 2. The torque sensor 15 outputs the detected torque to the progress state determination unit 22 in the ECU 11.

  The control start determination unit 21 in the ECU 11 determines whether or not to perform control for adjusting the damping ratio ζ based on the steering angle output from the steering angle sensor 14. When the control start determination unit 21 determines to start control, the control start determination unit 21 outputs a control start signal to the progress state determination unit 22.

  When the control start signal is output from the control start determination unit 21, the traveling state determination unit 22 determines whether the vehicle traveling state is in a straight traveling state or a turning state based on the torque output from the torque sensor 15. is doing. The progress state determination unit 22 outputs predetermined signals to the assist force control unit 23, the damping force control unit 24, and the friction force application control unit 25 based on the determination result.

  The assist force control unit 23 calculates a decrease amount of the assist force of the electric motor 12 based on the signal output from the progress state determination unit 22. The assist force control unit 23 outputs an assist signal for reducing the assist force of the electric motor 12 to the electric motor 12 based on the calculated decrease amount of the assist force.

  The damping force control unit 24 calculates the increase amount of the damping force of the electric motor 12 based on the signal output from the progress state determination unit 22. The damping force control unit 24 outputs a damping force signal for increasing the damping force of the electric motor 12 to the electric motor 12 based on the calculated increase amount of the damping force. Specifically, when this damping force signal is output to the electric motor 12, the motor torque of the electric motor 12 increases.

  The frictional force application control unit 25 calculates the amount of frictional force added to the steering shaft 3 by the frictional force applying unit 13 based on the signal output from the progress state determining unit 22. The frictional force imparting control unit 25 provides the frictional force imparting unit 13 with a frictional force signal for causing the frictional force imparting unit 13 to apply a physical frictional force to the steering shaft 3 based on the calculated additional amount of frictional force. Output.

  Next, the processing operation of the steering control device 10 according to the present embodiment will be described with reference to FIG.

FIG. 3 is a flowchart showing the processing operation of the steering control device 10. Table 1 is a table showing the processing operation of the steering control device 10 performed when the vibration frequency detected by the rudder angle sensor 14 is 10 Hz or more.

  The processing operation shown in FIG. 3 is repeatedly executed by the ECU 11 at predetermined intervals. First, the control start determination unit 21 checks the vibration frequency from the steering angle detected and output by the steering angle sensor 14 (S10). The control start determination unit 21 determines whether or not the checked vibration frequency is 10 Hz or more (S11).

  As a result, when it is determined that the vibration frequency is less than 10 Hz, vibration with a large frequency that is a suppression target is not generated. Therefore, the process is terminated without controlling the electric motor 12 or the like.

  On the other hand, when it is determined in step S <b> 11 that the vibration frequency is 10 Hz or higher, the control start determination unit 21 outputs a control start signal to the progress state determination unit 22. When the control start signal is input, the progress state determination unit 22 checks the steering torque output from the torque sensor 15 (S12). Then, based on the steering torque, it is determined whether or not the traveling state of the vehicle 1 is a straight traveling state (whether it is a turning state) in order to obtain the traveling state of the vehicle (S13).

  If the steering torque exceeds a predetermined threshold value, the steering wheel 2 is operated with a large torque, so that the traveling state is determined to be a turning state. On the other hand, when the steering torque is equal to or less than the predetermined threshold value, the steering wheel 2 is not operated with a very large steering torque, so that the traveling state is determined to be a straight traveling state.

  As a result of determining whether or not the vehicle is in the straight traveling state, when it is determined that the vehicle is in the straight traveling state, the assist force control unit 23 performs a decrease control of the assist force I (S14). Decreasing the assist force I increases the damping ratio ζ, as is apparent from the above equation (1), so that vibration of the steering system is suppressed. Here, in increasing the damping ratio ζ, the assist force I is decreased, while the damping force C of the electric motor 12 is set to a normal state and is not increased. Thus, by setting the damping force C to the normal state, it is possible to maintain the clarity that the steering wheel is positioned at the neutral position. If it is unclear that the vehicle is in the neutral position in the straight-ahead state, the steering feeling may feel awkward, but in the straight-ahead state, the assist force I is controlled to be reduced. It is possible to prevent the driver from feeling uncomfortable.

Note that the attenuation is more reliably suppressed by increasing the attenuation degree ζω that indicates the degree of attenuation. Here, the natural frequency ω can be expressed as ω = (K / I) ^1/2 . Increasing the assist force I decreases the natural frequency ω. For this reason, although the magnitude of the vibration is reduced, the degree of attenuation ζω is reduced, so that the vibration is small but the attenuation is poor and the vibration continues.

  In this respect, since the ECU 11 reduces the assist force I, the natural frequency ω increases and the resonance point of vibration shifts. In addition, since the degree of attenuation ζω is also increased, it is possible to prevent the deterioration of the attenuation and more suitably prevent the deterioration of the steering feeling.

  When it is determined in step S13 that the traveling state of the vehicle 1 is a turning state, the damping force control unit 24 performs an increase control of the damping force C (S15). Increasing the damping force C increases the damping ratio ζ, as is apparent from the above equation (1), so that the vibration of the steering system is suppressed. Here, in increasing the damping ratio ζ, while increasing the damping force, the assist force is not reduced in a normal state. In this way, by setting the assist force to a normal state, it is possible to reduce the force for the driver to give the steering force. When the assist force is reduced, the driver's labor when performing the turning operation is increased. In this regard, since the assist force is not reduced when the damping ratio ζ is increased, the steering of the steering wheel 2 during turning can be favorably assisted.

  Further, when the assist force I is decreased in step S14 and when the damping force C is increased in step S15, the frictional force imparting unit 13 supplements the physical frictional force on the steering shaft 3. Is given (S16). By applying a physical frictional force to the steering shaft 3, a feeling of viscosity during steering is suppressed, and vibration is more reliably suppressed. Furthermore, when the application of the frictional force is performed after the assist force I reduction control in step S14, the feeling of friction when the steering wheel is positioned at the neutral position is suppressed. Further, when the application of the frictional force is performed after the increase control of the damping force C in step S15, the return of the steering wheel 2 can be suppressed. Therefore, it is possible to suppress vibration transmitted to the driver without deteriorating the steering feeling regardless of whether the traveling direction of the vehicle 1 is a straight traveling state or a turning state.

  As described above, in the steering control device 10 according to the present embodiment, the assist force I is decreased when the vibration frequency is a predetermined frequency and the vehicle 1 is in a straight traveling state. Thereby, since the damping ratio ζ can be increased, vibration can be suppressed. Further, the damping force C of the electric motor 12 is kept in a normal state and is not increased, so that deterioration in steering feeling can be prevented. As a result, vibration can be suppressed without deteriorating the steering feeling. On the other hand, when the vibration frequency is a predetermined frequency and the vehicle 1 is turning, the damping force C of the electric motor 12 is increased. Thereby, since the damping ratio ζ can be increased, vibration can be suppressed. In addition, the assist force I of the electric motor 12 is set to a normal state and normal assist is performed, thereby preventing deterioration in steering feeling. As a result, vibration can be suppressed without deteriorating the steering feeling.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, in the above embodiment, the condition for starting the vibration suppression by the ECU 12 is the case where the vibration frequency obtained from the rudder angle detected by the rudder angle sensor 14 is 10 Hz or more in the above embodiment. The number of frequencies may be 10 Hz to 20 Hz.

  The condition for the frictional force application control unit 25 to control the frictional force application unit 13 is that the vibration at a predetermined vibration frequency is detected by the steering angle sensor 14 as described above, and the vibration continues for a predetermined time or more. It may be a case. Furthermore, in the above-described embodiment, control is performed to increase the damping force C during turning. However, for example, control is performed to increase the contribution of the frictional force applying unit 13 during turning to reduce the increase amount of the damping force C. You can also. In this way, by increasing the frictional force applied by the steering shaft 3 by reducing the increase in the damping force C, it is possible to cover the steering wheel return due to the increase in friction with the return control and effectively suppress the viscous feeling due to the damping. it can.

1 is a schematic configuration diagram of a vehicle including a steering control device according to the present embodiment. It is a block block diagram of a steering control apparatus. It is a flowchart which shows the processing operation of a steering control apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Steering wheel, 3 ... Steering shaft, 4 ... Pinion gear, 5 ... Rack shaft, 6 ... Tie rod, 7 ... Steering wheel, 10 ... Steering control apparatus, 12 ... Electric motor, 13 ... Friction force provision part , 14 ... rudder angle sensor, 15 ... torque sensor, 21 ... control start determination unit, 22 ... progress state determination unit, 23 ... assist force control unit, 24 ... damping force control unit, 25 ... friction force application control unit.

Claims (3)

In a steering control device that performs steering control of a running vehicle,
Frequency detection means for detecting a vibration frequency of the steering system of the vehicle;
A traveling state determining means for determining a traveling state of the vehicle;
A motor for applying assist force to the steering system of the vehicle;
Damping force control means for controlling the damping force of the motor,
The damping force control means increases the damping force of the motor when a predetermined vibration frequency is detected by the frequency detection means and when the traveling state determination means determines that the vehicle is turning. A steering control device characterized in that Assist force control means for controlling the assist force of the motor,
The assist force control means reduces the assist force of the motor when a predetermined vibration frequency is detected by the frequency detection means and when the traveling state determination means determines that the vehicle is in a straight traveling state. The steering control device according to claim 1 , wherein: 3. The steering control according to claim 1, further comprising a frictional force applying unit that applies a physical frictional force to the steering system when a predetermined vibration frequency is detected by the frequency detecting unit. apparatus.

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