Steering control device

Abstract

To provide a steering control device that can prevent deterioration in performance in recognizing a lane departure warning.SOLUTION: An assist control part 20 calculates estimated load torque Tx that is load torque acting on a steering shaft 95 of a steering system mechanism 100 and calculates an assist torque command Ta* so that steering torque Ts is made to follow target steering torque Ts* calculated on the basis of the estimated load torque Tx. 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 assist torque command Ta* and of the LDW control torque Tv*. A vibration amplitude setting part 50 sets vibration amplitude of the LDW control torque command Tv* to be larger as the assist torque command Ta* or the estimated load torque Tx is larger.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] 2. Description of the Related Art A steering control device that assists a driver's steering by using an assist torque output by a motor in a vehicle equipped with a lane keeping assist device is known.

[0003] For example, a vehicle steering device disclosed in Patent Document 1 superimposes a vibration torque for a lane departure warning on an assist torque. This vehicle steering device changes the magnitude of the vibration torque in response to the steering torque or the assist current as the steering state detected by a steering state detection unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-65587 A Summary of the Invention [Problem to be solved by the invention]

[0005] When driving on a bank, where the assist torque and road reaction force are greater than when driving straight ahead, the vibration component of the lane departure warning becomes smaller, making it more difficult for the driver to perceive the warning. When the vehicle speed increases while driving on a bank, the vibration of the lane departure warning becomes mixed up with the driving vibration, making it even more difficult for the driver to perceive it. Patent Document 1 discloses changing the magnitude of the vibration torque according to the detected value of the steering torque or the assist current, but does not disclose changing the magnitude of the vibration torque according to a value other than the detected value.

[0006] In addition, in a vehicle equipped with a lane keeping assist device in addition to a lane departure warning device, steering angle control is performed so that the steering angle follows the target steering angle. During operation of steering angle control by automatic steering, the steering angle based on the motor angle generated when the vibration torque of the lane departure warning is applied to drive the motor is corrected to the target steering angle. Therefore, the vibration appearing in the steering wheel becomes smaller than when the lane departure warning is activated during normal assistance, making it even more difficult for the driver to recognize the warning. Patent Document 1 does not mention anything related to such steering angle control.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a steering control device that prevents a decrease in the recognizability of a lane departure warning. [Means for solving the problem]

[0008] A first aspect of the present invention is a steering control device that assists a driver's steering with an assist torque output from a motor (80) connected to a steering mechanism (100) that generates a steering torque (Ts) in a vehicle equipped with a lane departure warning device (17). The steering control device of the first aspect includes an assist control unit (20), a vibration application control unit (50), a motor drive control unit (65), and a vibration amplitude setting unit (55).

[0009] The assist control unit calculates an estimated load torque (Tx) and sets a target steering torque (Ts * The assist torque command (Ta * The estimated load torque is a load torque acting on the steering shaft (95) of the steering system mechanism, and is estimated based on the balance between the road surface reaction force and the assist torque.

[0010] The vibration application control unit applies a lane departure warning control torque command (Tv *The motor drive control unit calculates the sum (Tm * ) to control the motor drive.

[0011] The vibration amplitude setting unit sets the vibration amplitude of the lane departure warning control torque command to a larger value as the assist torque command or the estimated load torque becomes larger. In the first aspect of the present invention, by using a value used for control calculation in the control device, it is possible to prevent a decrease in the driver's awareness of the warning when the assist torque or the estimated load torque is large.

[0012] A second aspect of the present invention is a steering control device that assists the driver's steering with an assist torque output by a motor (80) connected to a steering mechanism (100) that generates a steering torque (Ts) in a vehicle equipped with a lane keeping assist device (16) and a lane departure warning device (17). The steering control device of the second aspect includes an assist control unit (20), a steering angle control unit (30), a vibration application control unit (50), a motor drive control unit (65), and a vibration amplitude setting unit (55). The assist control unit and the vibration application control unit are the same as those of the first aspect.

[0013] The steering angle control unit converts the steering angle (θ) determined according to the output of the motor into a target steering angle (θ * ) to make the steering angle control torque command (Tθ * The motor drive control unit calculates the sum (Tm * ) to control the driving of the motor.

[0014] The vibration amplitude setting unit sets the vibration amplitude of the lane departure warning control torque command to be larger as the total value of the assist torque command and the steering angle control torque command or the total value of the estimated load torque and the steering angle control torque command is larger.

[0015] In the second aspect of the present invention, the magnitude of the steering angle control torque command in addition to the assist torque command or the estimated load torque is reflected in the vibration amplitude of the lane departure warning, thereby preventing a decrease in the driver's awareness of the warning while the lane keeping assist device is operating. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of an electric power steering system. [Diagram 2] 1 is a schematic configuration diagram of an EPS-ECU (steering control device) according to a first embodiment. [Diagram 3] FIG. 4 is a block diagram of a vibration amplitude setting unit. [Figure 4] 5 is a time chart showing the steering torque vibration amplitude in a comparative example and the first embodiment. [Diagram 5] FIG. 11 is a schematic configuration diagram of an EPS-ECU according to a second embodiment. [Figure 6] FIG. [Figure 7] FIG. 11 is a schematic configuration diagram of an EPS-ECU according to a third embodiment. [Figure 8] FIG. 13 is a schematic configuration diagram of an EPS-ECU according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, several embodiments of the steering control device will be described with reference to the drawings. In several embodiments, substantially the same configurations are given the same reference numerals and the description will be omitted. The first to fourth embodiments are collectively referred to as "the present embodiment." The steering control device of the present embodiment is applied to an electric power steering system of a vehicle equipped with a lane departure warning device. Moreover, the steering control device of the third and fourth embodiments is applied to an electric power steering system of a vehicle equipped with a lane keeping assist device.

[0018] In each embodiment, the LDW (Lane Departure Warning)-ECU corresponds to a "lane departure warning device," and the EPS-ECU corresponds to a "steering control device." LDW stands for lane departure warning. The LDW-ECU issues a warning to the driver when the vehicle is about to depart from the lane during driver steering or automatic steering. Instead of or in addition to an alarm sound or display, the LDW-ECU vibrates the steering wheel in cooperation with the EPS-ECU. The EPS-ECU assists the driver in steering by using the assist torque output by the motor.

[0019] In the third and fourth embodiments, the LKA (Lane Keep Assist)-ECU corresponds to the "lane keeping assist device." LKA stands for lane keeping assist. The LKA-ECU commands a target steering angle so that the vehicle maintains the lane in which it is traveling during automatic steering.

[0020] [Electric power steering system configuration] First, the configuration of an electric power steering system common to all the embodiments is shown in Fig. 1. Here, the LKA-ECU 16 used in the systems of the third and fourth embodiments is shown by a broken line. In the first and second embodiments, it is assumed that the LKA-ECU 16 is not necessary.

[0021] Basically, the electric power steering system 1 is a system that assists the driver in operating a steering wheel 91 by using the driving torque of a motor 80. The steering wheel 91 is fixed to one end of a steering shaft 92, and an intermediate shaft 93 is provided on the other end of the steering shaft 92. The steering shaft 92 and the intermediate shaft 93 are connected by a torsion bar of a torque sensor 94, and these constitute a steering shaft 95. The torque sensor 94 detects the steering torque Ts based on the torsion angle of the torsion bar.

[0022] A gear box 96 including a pinion gear 961 and a rack 962 is provided on the end of the intermediate shaft 93 opposite to the torque sensor 94. When the driver turns the steering wheel 91, the pinion gear 961 rotates together with the intermediate shaft 93, and the rack 962 moves left and right in accordance with the rotation of the pinion gear 961. Tie rods 97 provided on both ends of the rack 962 are connected to tires 99 via knuckle arms 98. The tie rods 97 reciprocate left and right, pulling and pushing the knuckle arms 98, thereby changing the orientation of the tires 99.

[0023] The motor 80 is, for example, a three-phase AC brushless motor, and outputs a driving torque according to a driving voltage Vd output from the EPS-ECU 15. In the case of a three-phase AC motor, the driving voltage Vd means each phase voltage of the U phase, the V phase, and the W phase. The rotation of the motor 80 is transmitted to an intermediate shaft 93 via a reduction mechanism 85 constituted by a worm gear 86, a worm wheel 87, etc. Furthermore, the rotation of the intermediate shaft 93 caused by the steering of a steering wheel 91 or a reaction force from the road surface is transmitted to the motor 80 via the reduction mechanism 85.

[0024] 1 is 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 this 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 separated. In other embodiments, a multi-phase AC motor other than a three-phase motor or a brushed DC motor may be used as the motor.

[0025] Here, the entire mechanism through which the steering force of the steering wheel 91 is transmitted from the steering wheel 91 to the tires 99 is referred to as the "steering system mechanism 100." The EPS-ECU 15 controls the driving torque output from the motor 80 to the steering system mechanism 100, thereby controlling the steering torque Ts generated by the steering system mechanism 100. The EPS-ECU 15 obtains the steering torque Ts and the steering angle θ from the steering system mechanism 100. The EPS-ECU 15 also obtains the vehicle speed V detected by a vehicle speed sensor 11 provided at a predetermined location on the vehicle.

[0026] In addition, the EPS-ECU 15 receives the target steering angle θ * and a steering angle control request flag F1 from the LDW-ECU 17, and obtains an LDW operation 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. For example, as is referred to in JP 2015-33942 A and the like, the LKA-ECU 16 sets a target course based on the driving lane and the position of the host vehicle detected from an image of an in-vehicle camera, and determines a target steering angle θ for traveling along the target course. * is output to EPS-ECU15.

[0027] As referred to in Patent Document 1 (JP 2017-65587 A) and the like, the LDW-ECU 17 determines whether or not there is a possibility of deviation from the lane or collision with an obstacle based on the steering angle, vehicle speed, video from an in-vehicle camera, yaw rate, lateral acceleration, etc. When it is determined that there is a possibility of deviation from the lane or collision with an obstacle, the LDW-ECU 17 outputs an LDW operation request flag F2 to the EPS-ECU 15.

[0028] The EPS-ECU 15 calculates each torque command, which will be described later, based on the acquired information, and drives the motor 80 by applying a drive voltage Vd to the motor 80 in accordance with the sum of the torque commands. The EPS-ECU 15 assists the steering of the driver with an assist torque Ta output by the motor 80. The various calculation processes in the EPS-ECU 15 may be software processes in which a CPU executes a program stored in advance in a physical memory device such as a ROM, or may be hardware processes in which a dedicated electronic circuit is used.

[0029] [EPS-ECU configuration] Next, the configuration of the EPS-ECU 15 of each embodiment will be described in order. The reference numeral of the EPS-ECU of each embodiment has the number of the embodiment added as the third digit following "15".

[0030] (First embodiment) The first embodiment will be described with reference to Fig. 2 to Fig. 4. As shown in Fig. 2, an EPS-ECU 151 of the first embodiment includes an assist control unit 20, a vibration application control unit 50, a motor drive control unit 65, and a vibration amplitude setting unit 55.

[0031] The assist control unit 20 outputs an assist torque command Ta in response to the steering torque Ts of the driver. * Specifically, the assist control unit 20 calculates the assist torque command Ta based on the steering torque Ts and the vehicle speed V so as to realize a transmission feeling according to the road reaction force (or road load) and a feel according to the steering state. * A more detailed configuration of the assist control unit 20 will be described later in the second embodiment.

[0032] When the LDW operation request is notified by the LDW-ECU 17 using the flag F2, the vibration application control unit 50 controls the LDW control torque command Tv so as to apply vibration to the assist torque. * Calculate the following.

[0033] The command adder 64 outputs the assist torque command Ta * , and LDW control torque command Tv* The final assist torque command Tm * and outputs the final assist torque command Tm * The motor 80 is driven by applying a drive voltage Vd to the motor 80 based on the final assist torque command Tm * The assist torque Ta corresponding to the above is output.

[0034] Each torque command Ta * , Tv * , Tm * The positive and negative of the torque is defined according to the rotation direction in which the torque is applied. For example, a torque applied in the left rotation direction is defined as positive, and a torque applied in the right rotation direction is defined as negative.

[0035] The above configuration is common to the EPS-ECU 152 of the second embodiment. Next, regarding the vibration amplitude setting unit 55, in the EPS-ECU 151 of the first embodiment, the assist torque command Ta * The vibration amplitude setting unit 55 receives the assist torque command Ta * The larger the LDW control torque command Tv * The vibration amplitude Amp of the LDW control torque command Tv is set large. * The vibration amplitude Amp of the laser diode warp is abbreviated to "LDW amplitude Amp."

[0036] 3, the vibration amplitude setting unit 55 includes an LDW basic amplitude setting unit 551, a correction gain map 552, and a multiplier 553. The LDW basic amplitude setting unit 551 sets the LDW basic amplitude. The LDW basic amplitude may be a fixed value or may be a variable value depending on, for example, the vehicle speed. Alternatively, the amplitude may be variable depending on an external input.

[0037] The correction gain map 552 specifies the relationship between the input and the correction gain. The torque parameter, which is the input, takes positive and negative values ​​depending on the direction of application, and the map is symmetrical between positive and negative, so the absolute value of the input may be represented on the horizontal axis. Basically, the larger the absolute value of the input, the larger the correction gain. However, a lower limit value that becomes a dead zone near the input of 0 is set, and an upper limit value is set in a range where the absolute value of the input is equal to or greater than a certain value. The multiplier 553 multiplies the LDW basic amplitude by the correction gain to output the LDW amplitude Amp.

[0038] The configuration of the vibration amplitude setting unit 55 shown in FIG. 3 is common to each embodiment, but the input torque parameter is different. In the first embodiment, the input torque parameter is the assist torque command Ta * In the second embodiment, it is the estimated load torque Tx. In the third embodiment, the assist torque command Ta * and steering angle control torque command Tθ * The sum of (Ta * +Tθ * In the fourth embodiment, the estimated load torque Tx and the steering angle control torque command Tθ * The sum of (Tx+Tθ * ).

[0039] Referring to FIG. 4, the assist torque command Ta * The effect of the first embodiment when the assist torque command Ta is increased will be described. The dimensions of each quantity on the vertical axis are torque ([Nm]). In the comparative example, * Even if the assist torque command Ta * Therefore, the driver's awareness of the warning is reduced.

[0040] In contrast, in the first embodiment, the assist torque command Ta * By increasing the LDW amplitude Amp as the steering torque increases, the vibration amplitude of the steering torque is kept constant. Therefore, it is possible to prevent the driver's awareness of the warning from deteriorating when the vehicle is traveling on a bank where the assist torque and road reaction force are large.

[0041] Second embodiment A second embodiment will be described with reference to Fig. 5 and Fig. 6. As shown in Fig. 5, an EPS-ECU 152 of the second embodiment has an assist torque command Ta * The vibration amplitude setting unit 55 inputs the estimated load torque Tx to the vibration amplitude setting unit 55. The vibration amplitude setting unit 55 increases the LDW control torque command Tv as the estimated load torque Tx increases. * The vibration amplitude Amp is set large.

[0042] 6, a description will be given of the estimated load torque Tx used in the control calculation of the assist control unit 20. The assist control unit 20 includes an estimated load torque calculation unit 22, a target steering torque calculation unit 23, and a steering torque servo controller .

[0043] The estimated load torque calculation unit 22 includes an adder 221 and a low-pass filter ("LPF" in the figure) 222. The adder 221 receives the assist torque command Ta * and the target steering torque Ts fed back from the target steering torque calculation unit 23. * and are added together. The low-pass filter 222 extracts a predetermined frequency component, for example a band of 10 Hz or less, from the added torque. The estimated load torque calculation unit 22 outputs the frequency component extracted by the low-pass filter 222 as an estimated load torque Tx. The estimated load torque Tx is a load torque acting on the steering shaft 95 of the steering system mechanism 100, and is estimated based on the balance between the road surface reaction force and the assist torque.

[0044] The target steering torque calculation unit 23 calculates the target steering torque Ts based on the estimated load torque Tx and the vehicle speed V. * The steering torque servo controller 24 calculates the target steering torque Ts calculated by the target steering torque calculation unit 23. * , and the steering torque Ts detected by the steering mechanism 100. The steering torque servo controller 24 converts the steering torque Ts into a target steering torque Ts * The assist torque command Ta *Calculate the following.

[0045] In this way, the assist control unit 20 calculates the estimated load torque Tx and calculates the target steering torque Ts * The assist torque command Ta is set to make the steering torque Ts follow the * Calculate the following.

[0046] In the second embodiment, the vibration amplitude setting unit 55 sets the LDW amplitude Amp to a larger value as the estimated load torque Tx increases, thereby making it possible to prevent a decrease in the driver's awareness of the warning, similarly to the first embodiment.

[0047] (Third and fourth embodiments) Next, a third and fourth embodiment will be described with reference to Fig. 7 and Fig. 8. As described above with reference to Fig. 1, the EPS-ECUs 153 and 154 of the third and fourth embodiments are applied to a vehicle equipped with the LKA-ECU 16 and the LDW-ECU 17. In the EPS-ECUs 153 and 154, the assist torque command Ta * , the steering angle control torque command Tθ by the steering angle control unit 30 * , and the LDW control torque command Tv by the vibration application control unit 50 * The added value Tm * Based on this, the motor drive control unit 65 controls the drive of the motor 80.

[0048] The steering angle θ determined according to the output of the motor 80 is fed back to the steering angle control unit 30. The steering angle control unit 30 receives the target steering angle θ commanded by the LKA-ECU 16 during the operation of the LKA control. * The steering angle control torque command Tθ is set to follow the steering angle θ. * The positive and negative steering angles θ are defined as, for example, an angle to the left of the neutral position being positive, and an angle to the right of the neutral position being negative.

[0049] The steering angle control unit 30 includes a steering angle deviation calculator 33 and a steering angle servo controller 34. The steering angle deviation calculator 33 calculates a target steering angle θ * and the steering angle θ.* The steering angle servo controller 34 calculates the target steering angle θ * In order to make the steering angle θ follow the steering angle θ, that is, to make the steering angle deviation Δθ approach 0, the steering angle control torque command Tθ is * Calculate the following.

[0050] The first command adder 61 outputs the assist torque command Ta * and steering angle control torque command Tθ * The second command adder 62 further adds the LDW control torque command Tv * By adding * and outputs it to the motor drive control unit 65. The above configuration is common to the EPS-ECUs 153, 154 of the third and fourth embodiments.

[0051] In the EPS-ECU 153 of the third embodiment shown in FIG. 7, the output of the first command adder 61, “assist torque command Ta * and steering angle control torque command Tθ * The vibration amplitude setting unit 55 inputs the assist torque command Ta * and steering angle control torque command Tθ * The sum of (Ta * +Tθ * ) is larger, the LDW control torque command Tv * The vibration amplitude Amp is set large.

[0052] In the EPS-ECU 154 of the fourth embodiment shown in Fig. 8, the estimated load torque Tx is output from the assist control unit 20 in the same manner as in the second embodiment. * The vibration amplitude setting unit 55 adds the estimated load torque Tx and the steering angle control torque command Tθ * The sum of (Tx+Tθ * ) is larger, the LDW control torque command Tv * The vibration amplitude Amp is set large.

[0053] During LKA control operation, LDW control torque command Tv * When the steering angle θ fluctuates due to the steering angle control, the steering angle control torque command Tθ is set to make the steering angle deviation Δθ approach 0. * As a result, the LDW control torque command Tv * The motor rotation angle resulting from the application of vibration at the motor 12 and the steering torque Ts resulting from the vibration are smaller than when the steering angle control is not in operation.

[0054] Therefore, in the third and fourth embodiments, the assist torque command Ta * Or, in addition to the estimated load torque Tx, the steering angle control torque command Tθ * The magnitude of the LDW vibration is reflected in the LDW vibration amplitude. Therefore, it is possible to prevent a decrease in the driver's awareness of the warning during the operation of the LKA control.

[0055] (Other embodiments) By combining the first and second embodiments, the vibration amplitude setting unit 55 sets the assist torque command Ta * The LDW amplitude Amp may be set based on an average value or a weighted average value of the estimated load torque Tx. * +Tθ * " and "Tx+Tθ * The LDW amplitude Amp may be set based on the value obtained from

[0056] The present invention is not limited to such an embodiment, and can be embodied in various forms without departing from the spirit of the present invention.

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

[0058] 15(151-154)···EPS-ECU (Steering Control Unit), 16···LKA-ECU (Lane Keeping Assist Device), 17···LDW-ECU (Lane Departure Warning System), 20 Assist control unit, 30...Steering angle control unit, 50... Vibration control unit, 65 Motor drive control unit, 80...Motor, 95···Steering shaft, 100···Steering system mechanism.

Claims

1. A steering control device for a vehicle equipped with a lane departure warning device (17) that assists a driver's steering with an assist torque (Ta) outputted by a motor (80) connected to a steering system mechanism (100) that generates a steering torque (Ts), The load torque acting on the steering shaft (95) of the steering system mechanism is calculated based on the balance between the road surface reaction force and the assist torque. A target steering torque (Ts * ) to make the steering torque follow the assist torque command (Ta * an assist control unit (20) for calculating When a request for activation of the lane departure warning is notified from the lane departure warning device, a lane departure warning control torque command (Tv * A vibration application control unit (50) that calculates The sum of the assist torque command and the lane departure warning control torque command (Tm * a motor drive control unit (65) for controlling the drive of the motor based on the a vibration amplitude setting unit (55) that sets a vibration amplitude of the lane departure warning control torque command to a larger value as the assist torque command or the estimated load torque becomes larger; A steering control device comprising:

2. A steering control device for a vehicle equipped with a lane keeping assist device (16) and a lane departure warning device (17) that assists a driver's steering with an assist torque (Ta) outputted by a motor (80) connected to a steering system mechanism (100) that generates a steering torque (Ts), The load torque acting on the steering shaft (95) of the steering system mechanism is calculated based on the balance between the road surface reaction force and the assist torque. A target steering torque (Ts * ) to make the steering torque follow the assist torque command (Ta * an assist control unit (20) for calculating The steering angle (θ) determined according to the output of the motor is set to the target steering angle (θ * ) so as to make the steering angle control torque command (Tθ * A steering angle control unit (30) for calculating When a request for activation of the lane departure warning is notified from the lane departure warning device, a lane departure warning control torque command (Tv * A vibration application control unit (50) that calculates The sum of the assist torque command, the steering angle control torque command, and the lane departure warning control torque command (Tm * a motor drive control unit (65) for controlling the drive of the motor based on the a vibration amplitude setting unit (55) that sets a vibration amplitude of the lane departure warning control torque command to a larger value as the sum of the assist torque command and the steering angle control torque command or the sum of the estimated load torque and the steering angle control torque command increases; A steering control device comprising:

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