Steering control device

Abstract

To provide a steering control device that can prevent deterioration in performance in recognizing a lane departure warning during steering angle control performed by lane keeping assist control.SOLUTION: An assist control part 20 calculates an assist torque command Ta* on the basis of steering torque Ts. A steering angle control part 301 calculates a steering angle control torque command Tθ* so that a steering angle θ determined in accordance with output of a motor 80 is made to follow a target steering angle θ* commanded from an LKA-ECU (a lane keeping assist device) 16. A vibration application control part 50 calculates an LDW control torque command Tv* so that vibrations are applied to assist torque, when receiving a notice of an LDW operation request from an LDW-ECU (a lane departure warning device) 17. A motor driving control part 65 controls driving of the motor 80 on the basis of additional values Tm* of the torque commands Ta*, Tθ* and Tv*. The steering angle control part 30 has a vibration removal filter 401 that removes vibration frequency components of an LDW, during calculation on a steering angle signal loop for steering angle control.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a steering control device.

Background Art

[0002] Conventionally, in a vehicle equipped with a lane keeping support device, a steering control device that assists a driver's steering with assist torque output by a motor is known.

[0003] For example, the vehicle steering device disclosed in Patent Document 1 superimposes the vibration torque of a lane departure warning on the assist torque and changes the magnitude of the vibration torque according to the driver's steering state.

[0004] In the motor control device disclosed in Patent Document 2, a target tracking control calculation unit calculates a following control for following the target steering angle commanded from the lane keeping support device, that is, a steering torque command for steering the steering angle by automatic steering. The motor control device drives the motor according to the added value of the assist torque command for reducing the steering load and the steering torque command for the steering angle of automatic steering, and reduces the responsiveness of the automatic steering when detecting an intervention by the driver.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] During the operation of the steering angle control by automatic steering, the steering angle based on the motor angle generated when driving the motor by applying the vibration torque of the lane departure warning is corrected so as to become the target steering angle. Steering angle control The imperial In order to cancel the vibration of the lane departure warning, the vibration that appears on the steering wheel during the operation of the lane departure warning is smaller than that during normal assist, making it difficult for the driver to recognize the warning.

[0007] The present invention was created in view of such points, and its purpose is to provide a steering control device that prevents a decrease in the recognizability of a lane departure warning during the operation of steering angle control by lane keeping assist control.

Means for Solving the Problem

[0008] The present invention is a steering control device that assists a driver's steering by assist torque output from a motor (80) in a vehicle equipped with a lane keeping assist device (16) and a lane departure warning device (17). This steering control device includes an assist control unit (20), a steering angle control unit (30), a vibration application control unit (50), and a motor drive control unit (65).

[0009] The assist control unit calculates an assist torque command (Ta * ) based on the steering torque (Ts). The steering angle control unit calculates a steering angle control torque command (Tθ * ) so that the steering angle (θ) determined according to the output of the motor follows the target steering angle (θ * ) commanded from the lane keeping assist device.

[0010] When a lane departure warning activation request is notified from the lane departure warning device, the vibration application control unit calculates a lane departure warning control torque command (Tv * ) to apply vibration to the assist torque.

[0011] The motor drive control unit controls the drive of the motor based on the sum value (Tm * ) of the assist torque command, the steering angle control torque command, and the lane departure warning control torque command.

[0012] The steering angle control unit has a vibration removal filter (40) that removes the vibration frequency component of the lane departure warning within the calculation on the steering angle signal loop of the steering angle control.is such that the rudder angle control does not cancel out the vibration of the lane departure warning It is.

[0013] In the present invention, when the steering angle control by the lane keeping support control is operating, by not suppressing the motor angle variation of the vibration frequency of the lane departure warning, it is possible to generate a desired vibration torque of the lane departure warning. Therefore, even when the lane keeping support control is operating, the driver can recognize the warning.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

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Figure 10

Embodiments for Carrying Out the Invention

[0015] Hereinafter, an embodiment of the steering control device will be described with reference to the drawings. The steering control device of this embodiment is applied to an electric power steering system of a vehicle equipped with a lane keeping support device and a lane departure warning device. In one embodiment, the EPS-ECU corresponds to the "steering control device". Also, the LKA (Lane Keep Assist)-ECU corresponds to the "lane keeping support device", and the LDW (Lane Departure Warning)-ECU corresponds to the "lane departure warning device". LKA control means lane keeping support control, and LDW control means lane departure warning control.

[0016] The LKA-ECU commands a target steering angle so as to maintain the lane in which the vehicle travels during automatic steering. The LDW-ECU issues a warning to the driver when the vehicle is about to deviate from the lane during driver steering or automatic steering. In this embodiment, instead of or in addition to an alarm sound and a display, the EPS-ECU vibrates the steering wheel in cooperation with it. The EPS-ECU assists the driver's steering with the assist torque output by the motor.

[0017] [Configuration of Electric Power Steering System] As shown in FIG. 1, basically, the electric power steering system 1 is a system that assists the operation of the steering wheel 91 by the driver with the driving torque of the motor 80. A steering wheel 91 is fixed to one end of the steering shaft 92, and an intermediate shaft 93 is provided on the other end side of the steering shaft 92. The steering shaft 92 and the intermediate shaft 93 are connected by the torsion bar of the torque sensor 94, and these constitute the steering axis 95. The torque sensor 94 detects the steering torque Ts based on the twist angle of the torsion bar.

[0018] On the end of the intermediate shaft 93 opposite to the torque sensor 94, a gear box 96 including a pinion gear 961 and a rack 962 is provided. When the driver turns the steering wheel 91, the pinion gear 961 rotates together with the intermediate shaft 93, and as the pinion gear 961 rotates, the rack 962 moves left and right. Tie rods 97 provided at both ends of the rack 962 are connected to the tire 99 via knuckle arms 98. The tie rods 97 reciprocate left and right, pulling and pushing the knuckle arms 98, thereby changing the direction of the tire 99.

[0019] The motor 80 is, for example, a three-phase AC brushless motor, and outputs drive torque according to the drive voltage Vd output from the EPS-ECU 15. In the case of a three-phase AC motor, the drive voltage Vd means the phase voltages of each of the U-phase, V-phase, and W-phase. The rotation of the motor 80 is transmitted to the intermediate shaft 93 via a speed reduction mechanism 85 constituted by a worm gear 86, a worm wheel 87, and the like. Also, the rotation of the intermediate shaft 93 due to the steering of the steering wheel 91 or the reaction force from the road surface is transmitted to the motor 80 via the speed reduction mechanism 85.

[0020] Note that the electric power steering system 1 shown in FIG. 1 is of a column assist type in which the rotation of the motor 80 is transmitted to the steering shaft 95, but the EPS-ECU 15 of the present embodiment is also applicable to a rack assist type electric power steering system or a steer-by-wire system in which the steering wheel and the steered wheels are mechanically disconnected. Also, in other embodiments, a polyphase AC motor other than three-phase or a DC motor with brushes may be used as the motor.

[0021] Here, the entire mechanism through which the steering force of the steering wheel 91 is transmitted from the steering wheel 91 to the tire 99 is referred to as the "steering system mechanism 100". The EPS-ECU 15 controls the steering torque Ts generated by the steering system mechanism 100 by controlling the drive torque output by the motor 80 to the steering system mechanism 100. The EPS-ECU 15 acquires the steering torque Ts and the steering angle θ from the steering system mechanism 100. Further, the EPS-ECU 15 acquires the vehicle speed V detected by the vehicle speed sensor 11 provided at a predetermined part of the vehicle.

[0022] Further, the EPS-ECU 15 acquires the target steering angle θ * and the steering angle control request flag F1 from the LKA-ECU 16, and acquires the LDW activation request flag F2 from the LDW-ECU 17. During automatic steering, the LKA-ECU 16 outputs the steering angle control request flag F1 to the EPS-ECU 15. As referred to in Patent Document 2 (Japanese Patent Laid-Open No. 2015-33942) and the like, the LKA-ECU 16 sets a target course based on the driving lane detected from the image of the in-vehicle camera and the position of the host vehicle, and the target steering angle θ * for traveling along the target course is output to the EPS-ECU 15.

[0023] The LDW-ECU 17 determines whether there is a possibility of deviating from the lane or colliding with an obstacle based on the steering angle, vehicle speed, image of the in-vehicle camera, yaw rate, lateral acceleration, etc., as referred to in Patent Document 1 (Japanese Patent Laid-Open No. 2017-65587) and the like. When it is determined that there is a possibility of lane departure or collision with an obstacle, the LDW-ECU 17 outputs the LDW activation request flag F2 to the EPS-ECU 15.

[0024] The EPS-ECU 15 operates on the power from an in-vehicle battery (not shown) and calculates each torque command described later based on the acquired information. The EPS-ECU 15 drives the motor 80 by applying a drive voltage Vd to the motor 80 according to the added value of each calculated torque command. Note that various arithmetic processes in the EPS-ECU 15 may be software processes in which a program pre-stored in a physical memory device such as a ROM is executed by a CPU, or may be hardware processes by a dedicated electronic circuit.

[0025] [Configuration of EPS-ECU] (One Embodiment) FIG. 2 shows a conceptual configuration of the EPS-ECU 15 of the present embodiment. In the EPS-ECU 15, an assist torque command Ta by the assist control unit 20 * , a steering angle control torque command Tθ by the steering angle control unit 30 * , and an LDW control torque command Tv by the vibration applying control unit 50 * are added to obtain a value Tm * , based on which the motor drive control unit 65 controls the drive of the motor. The steering angle θ determined according to the output of the motor is fed back to the steering angle control unit 30.

[0026] The assist control unit 20 calculates an assist torque command Ta according to the steering torque Ts of the driver. * The steering angle control unit 30 calculates a steering angle control torque command Tθ * so that the steering angle θ follows the target steering angle θ * commanded from the LKA-ECU 16. The vibration applying control unit 50 calculates an LDW control torque command Tv * to apply vibration to the assist torque when an LDW operation request is notified from the LDW-ECU 17 by a flag F2.

[0027] The steering angle control unit 30 has a vibration removal filter 40 that removes the vibration frequency component of the LDW within the calculation on the steering angle signal loop of the steering angle control.

[0028] Fig. 3 shows the specific configuration of the EPS-ECU 15. Since the arrangement of the vibration removal filter in the steering angle control unit is an example, in Fig. 3, "steering angle control unit 301" and "vibration removal filter 401" are denoted instead of the comprehensive reference signs "steering angle control unit 30" and "vibration removal filter 40" in Fig. 2. Another arrangement example of the vibration removal filter in the steering angle control unit is shown in Fig. 10(a) and Fig. 10(b).

[0029] Each torque command Ta * , Tθ * , Tv * , Tm * The positive and negative of are defined according to the rotational direction to which the torque is applied. For example, the torque applied in the left rotation direction is defined as positive, and the torque applied in the right rotation direction is defined as negative. The positive and negative of the steering angle θ are defined such that, for example, the angle on the left side with respect to the neutral position is positive, and the angle on the right side with respect to the neutral position is negative.

[0030] The EPS-ECU 15 includes an assist control unit 20, a steering angle control unit 30, a vibration application control unit 50, a motor drive control unit 65, etc. Although there is some overlap with the description of Fig. 2, the configuration of each unit will be described in more detail. The assist control unit 20 calculates an assist torque command Ta * so that a transmission feeling according to the road surface reaction force (or road surface load) and a feel according to the steering state are realized based on the steering torque Ts and the vehicle speed V.

[0031] The steering angle control unit 30 has a steering angle deviation calculator 33, a steering angle servo controller 34, and a vibration removal filter 401. The steering angle deviation calculator 33 calculates a steering angle deviation Δθ (= θ * - θ) between the target steering angle θ * commanded from the LKA-ECU 16 and the steering angle θ.

[0032] The steering angle servo controller 34 has a PID calculator 36 including a proportional calculator 361, an integral calculator 362, a differential calculator 363, and an adder 364. Kp, Ki, and Kd in the figure are the proportional gain, integral gain, and differential gain, respectively, s is the Laplace operator, and τ is the time constant. The steering angle servo controller 34 controls the target steering angle θ *The rudder angle control torque command Tθ is calculated by PID control so as to follow the rudder angle θ, that is, to make the rudder angle deviation Δθ approach 0. * is calculated.

[0033] The vibration removal filter 401 shown in FIG. 3 is provided in the input path of the rudder angle signal among the "calculations on the rudder angle signal loop of the rudder angle control", and the filtered rudder angle θ_flt is input to the rudder angle deviation calculator 33. As will be described in detail later, the vibration removal filter 401 removes the vibration frequency components of the LDW.

[0034] When the LDW operation request flag F2 is input from the LDW-ECU 17 to the vibration application control unit 50, the LDW control torque command Tv is calculated to apply vibration to the assist torque to alert the driver. * is calculated.

[0035] The command adder 60 calculates the final assist torque command Tm, which is the sum of the assist torque command Ta * , the rudder angle control torque command Tθ * , and the LDW control torque command Tv * , and outputs it to the motor drive control unit 65. The motor drive control unit 65 drives the motor 80 by applying a drive voltage Vd to the motor 80 according to the final assist torque command Tm * . Thereby, the motor 80 outputs an assist torque Ta corresponding to the final assist torque command Tm * . *

[0036] Referring to FIG. 4, the operation of the vibration removal filter 401 with respect to the rudder angle signal will be described. The dashed line indicates the rudder angle signal input to the rudder angle deviation calculator 33 when there is no vibration removal filter, and the solid line indicates the case when the vibration removal filter 401 is used.

[0037] When the vibration removal filter is not used, when the rudder angle θ swings due to the LDW control torque command Tv * , in the rudder angle control, the rudder angle control torque command Tθ is adjusted to make the rudder angle deviation Δθ between the target rudder angle θ * and the rudder angle θ approach 0. *is calculated. As a result, the LDW control torque command Tv * The motor rotation angle, which is the result of applying vibration at * , and furthermore the resulting steering torque Ts become smaller compared to when the steering angle control is not operating.

[0038] On the other hand, when using the steering angle signal processed by the vibration removal filter 401, since the steering angle control recognizes that there is no vibration or the vibration is small for the steering angle control, interference of the steering angle control with respect to the vibration applied by the LDW control is prevented. As a result, the vibration of the steering torque Ts can be generated without change compared to normal assist. Therefore, the driver can recognize the warning.

[0039] Subsequently, the frequency characteristics of the vibration removal filter will be described. In this part, "40" is comprehensively used as the symbol of the vibration removal filter. The control band of the steering angle control by the LKA control is, for example, a band from direct current to 5 Hz or less. Compared with this band, the vibration frequency of the LDW is set to a high frequency band (for example, around 20 Hz) such that a person can recognize it as a warning. The vibration removal filter 40 used in the steering angle control has a characteristic of attenuating the gain near the vibration frequency of the LDW.

[0040] Examples of the frequency characteristics of the vibration removal filter 40 are shown in FIGS. 5 and 6. The vibration removal filter 40 in the example shown in FIG. 5 is composed of a notch filter that attenuates a specific frequency component. The vibration removal filter 40 in the example shown in FIG. 6 is composed of a filter that reduces the gain of a specific frequency or higher to a predetermined level. Specifically, for example, a plurality of stages of first-order lag filters are arranged in series.

[0041] For example, for a steering angle control band of 5 Hz or less, the LDW vibration band is around 20 Hz. Thus, the vibration frequency of the LDW is set to a higher frequency band than the frequency band used for the steering angle control. The gain in the steering angle control band is 1, and the vibration removal filter 40 passes the frequency components in the band of the steering angle control as they are.

[0042] Next, referring to the time charts of FIGS. 7 to 9, the behavior when the LDW control is activated will be described. Here, a case is simulated where the vehicle is traveling straight at 100 km / h and the LDW control vibration is applied three times. From the top in each figure, the LDW control torque command, the assist torque, the steering torque, and the steering angle are shown in order.

[0043] As shown in FIG. 7, when the LDW control is activated during normal assist by the driver's steering, the steering torque and the steering angle vary at a level that allows the driver to easily recognize the warning.

[0044] As shown in FIG. 8, in the comparative example without the vibration removal filter, when the LDW control is activated during the LKA control, the variations in the steering torque and the steering angle are small. Regarding the steering torque, due to the interference of the LKA control, the vibration applied by the LDA control becomes small, and it becomes difficult for the driver to recognize the warning amidst the road surface vibrations during driving. Also, regarding the steering angle, the steering angle is maintained by the steering angle control so as to follow the command of 0 deg which is the target steering angle of the LKA control.

[0045] As shown in FIG. 9, in the present embodiment using the vibration removal filter 40, when the LDW control is activated during the LKA control, the variation in the steering torque Ts is larger than that in the comparative example of FIG. 8. That is, by using the vibration removal filter 40, vibrations comparable to those during normal assist can be generated. Therefore, the driver can recognize the warning.

[0046] As described above, in the present embodiment, by not suppressing the motor angle variation of the LDW vibration frequency when the steering angle control by the LKA control is activated, a desired LDW vibration torque can be generated. Therefore, even when the LKA control is activated, the driver can recognize the warning.

[0047] Also, the vibration frequency of the LDW is set in a frequency band higher than the frequency band used for the steering angle control, and the vibration removal filter 40 passes the frequency components of the steering angle control band as they are. Therefore, the followability of the steering angle control is ensured without deterioration.

[0048] Note that Patent Document 1 describes a technique in which the larger the steering torque of the driver, the larger the LDW vibration torque is made, making it easier for the driver to recognize the warning. For example, based on this technique, a method of increasing the vibration amplitude of the LDW when the steering angle control is activated in automatic steering is assumed.

[0049] However, as the servo ability of the steering angle control increases, it becomes necessary to make the vibration amplitude extremely large. Then, there are concerns that the stability of the system may be impaired and the convergence of the vibration may deteriorate, or the vibration amplitude may become inappropriate during the transition process when the steering angle control is interrupted due to a failure or the driver's override operation.

[0050] In contrast, this embodiment suppresses the influence on the LDW control by the steering angle control by not changing the vibration amplitude itself of the LDW and only reducing the followability in a specific frequency band in the steering angle control. Therefore, it is possible to avoid a decrease in the stability of the system and inappropriate vibration generation during the transition process of the steering angle control.

[0051] (Other Embodiments) (1) The steering angle control unit of the present invention only needs to have a vibration removal filter "inside the calculation on the steering angle signal loop of the steering angle control". Configuration examples of the steering angle control unit in other embodiments different from the steering angle control unit 301 shown in FIG. 3 are shown in FIGS. 10(a) and 10(b).

[0052] The steering angle control unit 302 shown in FIG. 10(a) has a vibration removal filter 402 between the steering angle deviation calculator 33 and the steering angle servo controller 34. The vibration removal filter 402 removes the components in the LDW vibration frequency band included in the steering angle deviation Δθ.

[0053] The steering angle control unit 303 shown in FIG. 10(b) has a vibration removal filter 403 on the output side of the steering angle servo controller 34. The vibration removal filter 403 outputs the steering angle control torque command Tθ * from which the components in the LDW vibration frequency band are removed. Thereby, the influence of the steering angle control on the vibration applied in the LDW control is suppressed.

[0054] In any of the rudder angle control units 301 to 303 shown in FIGS. 3, 10(a), and 10(b), by suppressing the interference with the LDW control, the vibration of the steering torque Ts can be generated in the same manner as during normal assistance. Therefore, the driver can recognize the warning. Further, not limited to the configurations of FIGS. 10(a) and 10(b), a vibration removal filter may be used for either one or both of the proportional term or the derivative term of the PID calculator 36 that has a high contribution degree to the LDW vibration.

[0055] (2) The frequency characteristics of the vibration removal filter 40 are not limited to those illustrated in FIGS. 5 and 6. Instead of the series arrangement configuration of a plurality of first-order lag filters, for example, a filter that calculates in the form of an integrated transfer function may be used. As long as at least the components in the LDW vibration frequency band can be removed, a filter with any characteristics may be used regardless of the relationship with the frequency band of the rudder angle control.

[0056] The present invention is not limited to such embodiments, and can be implemented in various forms without departing from the spirit thereof.

[0057] The control unit and its method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit and its method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Or, the control unit and its method described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured by one or more hardware logic circuits. Also, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer.

Explanation of Symbols

[0058] 15 ··· EPS-ECU (Steering Control Device), 16 ··· LKA-ECU (Lane Keeping Support Device), 17 ··· LDW-ECU (Lane Departure Warning Device), 20 ··· Assist Control Unit, 30(301 - 303) ··· Steering Angle Control Unit, 40(401 - 403) ··· Vibration Removal Filter, 50 ··· Vibration Application Control Unit, 65 ··· Motor Drive Control Unit, 80 ··· Motor.

Claims

1. In a vehicle equipped with a lane keeping support device (16) and a lane departure warning device (17), a steering control device that assists the driver's steering by assist torque output by a motor (80), An assist control unit (20) that calculates an assist torque command (Ta ＊ based on the steering torque (Ts); The steering angle (θ) determined according to the output of the motor is made to follow the target steering angle (θ ＊ ) of a steering angle control torque command (Tθ ＊ ) is calculated by a steering angle control unit (30), When an operation request for a lane departure warning is notified from the lane departure warning device, a vibration application control torque command (Tv ＊ ) for calculating a vibration is applied to the assist torque, and a vibration application control unit (50); The added value (Tm ＊ ) of the assist torque command, the steering angle control torque command, and the lane departure warning control torque command, and a motor drive control unit (65) that controls driving of the motor based on comprising: The steering angle control unit has a vibration removal filter (40) that removes the vibration frequency component of the lane departure warning within the calculation on the steering angle signal loop of the steering angle control, so that the steering angle control does not cancel the vibration of the lane departure warning. Steering control device.

2. The vibration frequency of the lane departure warning is set in a frequency band higher than the frequency band used for steering angle control, The steering control device according to claim 1, wherein the vibration removal filter passes the frequency components of the steering angle control band as they are.

3. The steering control device according to claim 1 or 2, wherein the vibration removal filter is constituted by a notch filter that attenuates specific frequency components.

4. The steering control device according to claim 1 or 2, wherein the vibration removal filter is constituted by a filter that reduces the gain of a specific frequency or higher to a predetermined level.

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