Vehicle behavior estimation method, vehicle behavior detection device, and steering system

Abstract

A vehicle behavior estimation method, a vehicle behavior detection device, and a steering system according to one embodiment of the present invention are provided with a motor for applying steering torque to wheels via a movable member. A first deviation is output by comparing a standard traveling state of a vehicle obtained from steering operation information of a driver with an actual traveling state of the vehicle. A second deviation is output by comparing a standard axial force generated in the movable member, which is obtained from a traveling speed of the vehicle and a steering angle of a wheel, with an estimated axial force generated in the movable member, which is obtained from a current value of the motor. The behavior of the vehicle is estimated by comparing the first deviation to the second deviation. Therefore, the detection precision of the vehicle behavior can be improved.

Description

Technical Field

[0001] The present invention relates to a vehicle behavior estimation method, a vehicle behavior detection device and a steering system. Background Art

[0002] The vehicle turning behavior control device of Patent Document 1 calculates a target yaw rate based on a steering angle and a vehicle speed, and determines an understeer state when an actual yaw rate input from a yaw rate sensor is lower than the target yaw rate, and determines an oversteer state when the actual yaw rate is higher than the target yaw rate.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-093489 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, when understeer or oversteer as vehicle behavior is detected based on a yaw rate deviation, which is the deviation between a standard yaw rate calculated based on the steering angle of the wheels, the vehicle speed, etc. and the yaw rate actually generated in the vehicle, a yaw rate deviation may also occur due to disturbances such as unevenness of the road surface on which the vehicle is traveling.

[0008] Therefore, in the detection of the vehicle behavior based on the yaw rate deviation, there is a problem that the detection accuracy is reduced due to the interference.

[0009] The present invention is made in view of the actual situation in the past, and its purpose is to provide a vehicle behavior estimation method, a vehicle behavior detection device and a steering system that can improve the detection accuracy of vehicle behavior.

[0010] Means for solving problems

[0011] The vehicle behavior estimation method, vehicle behavior detection device and steering system involved in the present invention, in one mode, calculate the standard driving state of the vehicle based on the steering operation information of the vehicle driver, compare the standard driving state with the driving state actually generated in the vehicle and output a first deviation, calculate the standard axial force generated in the movable part based on a first physical quantity related to the driving speed of the vehicle and a second physical quantity related to the steering angle of the wheel, calculate the estimated axial force generated in the movable part based on a third physical quantity related to the current value of the motor, compare the standard axial force with the estimated axial force and output a second deviation, and estimate the behavior of the vehicle by comparing the first deviation with the second deviation.

[0012] Effects of the Invention

[0013] According to the present invention, the detection accuracy of vehicle behavior can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of a vehicle having a steer-by-wire steering system.

[0015] Figure 2 It is a functional block diagram representing the process of estimating vehicle behavior.

[0016] Figure 3 1 is a time chart illustrating changes in the yaw rate deviation and the axial force deviation in an uneven region of the road surface. DETAILED DESCRIPTION

[0017] Hereinafter, embodiments of a vehicle behavior estimation method, a vehicle behavior detection device, and a steering system according to the present invention will be described with reference to the accompanying drawings.

[0018] Figure 1 1 is a schematic diagram showing one embodiment of a vehicle 100 equipped with a steer-by-wire steering system 200 .

[0019] The vehicle 100 is a four-wheeled vehicle including a pair of left and right front wheels 101 , 102 and a pair of left and right rear wheels 103 , 104 .

[0020] The steering system 200 includes: a steering operation input device 300, to which the steering operation of the driver of the vehicle 100 is input via a steering wheel (steering wheel) 310; a steering device 400, which includes a steering motor 410 that applies a steering torque to the wheels of the vehicle 100 (specifically, m, front wheels 101, 102); and a steering control device 500.

[0021] Here, the steering operation input device 300 and the steering device 400 are mechanically separated.

[0022] The steering operation input device 300 includes a steering wheel 310 , a steering shaft 320 , a reaction force motor 330 , and an operation angle sensor 340 .

[0023] The steering wheel 310 is a steering operation input member operated by the driver of the vehicle 100 .

[0024] The reaction force motor 330 is an actuator for applying a steering reaction force torque to the steering wheel 310 in a pseudo manner.

[0025] The operation angle sensor 340 is a sensor that detects the operation angle θ [deg] of the steering wheel 310 .

[0026] The steering device 400 includes a steering mechanism 420 .

[0027] The steering mechanism 420 converts the rotational motion of the steering motor 410 into the linear motion of a rack bar 421 by a rack and pinion method, thereby changing the steering angle of the front wheels 101 and 102 .

[0028] That is, the steering motor 410 applies the steering torque to the front wheels 101 and 102 via the rack bar 421 which is a movable member.

[0029] In addition, the steering device 400 includes a rack stroke sensor 430 that detects a rack stroke RS [mm], which is a stroke amount of the rack rod 421 related to the steering angle of the front wheels 101 , 102 , a motor rotation angle sensor 440 that detects a rotation angle θm [deg] of the steering motor 410 , and a motor current sensor 450 that detects a current value Cm [Arms] of the steering motor 410 .

[0030] The steering control device 500 is an electronic control device including an MCU (Micro Controller Unit) 510 , and controls the operation of the steering system 200 by controlling the reaction force motor 330 and the steering motor 410 which are actuators included in the steering system 200 .

[0031] In addition, the MCU 510 can be alternatively referred to as a microcomputer, a processor, a processing device, a computing device, etc.

[0032] The MCU 510 calculates a control signal for the reaction force motor 330 and a control signal for the steering motor 410 by performing calculation processing on various signals acquired from the outside, and outputs the calculated control signals.

[0033] Here, the steering control device 500 may include a pre-driver, an inverter, and the like for controlling energization of the reaction force motor 330 and the steering motor 410 .

[0034] Furthermore, it is possible to provide a system including a drive circuit including a pre-driver, an inverter, and the like, separately from the steering control device 500 .

[0035] In addition, the vehicle 100 has wheel speed sensors 621-624 for detecting the rotation speeds of the wheels 101-104, namely the wheel speeds WS1-WS4, a longitudinal acceleration sensor 630 for detecting the acceleration G in the longitudinal direction of the vehicle 100, and a yaw rate sensor 640 for detecting the yaw rate γ [deg / s] generated in the vehicle 100.

[0036] Furthermore, the MCU 510 of the steering control device 500 obtains output signals of the operation angle sensor 340 , the rack stroke sensor 430 , the motor rotation angle sensor 440 , the motor current sensor 450 , the wheel speed sensors 621 - 624 , the longitudinal acceleration sensor 630 , and the yaw rate sensor 640 .

[0037] Here, the control contents of the steering system 200 (specifically, the reaction force motor 330 and the steering motor 410 ) performed by the MCU 510 of the steering control device 500 will be summarized.

[0038] The MCU 510 calculates a target rack stroke RStg (in other words, a target value of the steering angle) which is a target value of the stroke amount of the rack bar 421 based on information on the operation angle θ of the steering wheel 310 .

[0039] Then, the MCU 510 obtains a control signal for the steering motor 410 based on the deviation between the actual rack stroke RS detected by the rack stroke sensor 430 and the target rack stroke RStg, that is, the control error of the steering angle, and outputs the obtained control signal to the driving circuit of the steering motor 410 .

[0040] In the present embodiment, the rack stroke sensor 430 is used to detect the actual rack stroke RS. However, the actual rack stroke RS may be obtained by calculating the stroke amount of the rack bar 421 based on the motor rotation angle θm detected by the motor rotation angle sensor 440 .

[0041] Alternatively, the actual rack stroke RS may be obtained by using a detector that is provided on a pinion gear and detects the rotation angle of a pinion shaft.

[0042] Furthermore, the MCU 510 calculates a reaction torque command value TRtg which is a target value of the reaction torque TR based on information such as the vehicle speed VS [km / h] obtained from the wheel speeds WS1 to WS4 and the operation angle θ of the steering wheel 310 .

[0043] In addition, the MCU 510 can obtain the signals of the wheel speeds WS1 - WS4 from the wheel speed sensors 621 - 624 to obtain the vehicle speed VS. Furthermore, other vehicle control devices can obtain information on the vehicle speed VS obtained based on the signals of the wheel speeds WS1 - WS4 via the vehicle network.

[0044] Then, the MCU 510 outputs a control signal based on the reaction force torque command value TRtg to the drive circuit of the reaction force motor 330 .

[0045] In this way, the MCU 510 controls the operation of the steering system 200 by controlling the steering torque applied to the front wheels 101 and 102 and the reaction torque applied to the steering wheel 310 .

[0046] Furthermore, the MCU 510 has a function of estimating the vehicle behavior in accordance with a prescribed procedure and performing vehicle behavior notification of notifying the driver of the vehicle 100 of the estimated vehicle behavior.

[0047] That is, the MCU 510 is a control unit that executes the vehicle behavior estimation method and constitutes the vehicle behavior detection device.

[0048] Here, the vehicle behavior is understeering (U / S) or oversteering (O / S) as the turning behavior of the vehicle 100 .

[0049] In the steer-by-wire steering system 200 , even if the vehicle 100 understeers or oversteers, the steering force of the steering wheel 310 does not change, so it is difficult for the driver to recognize understeer or oversteer.

[0050] Therefore, the MCU 510 estimates whether the vehicle 100 is understeering or oversteering, and warns the driver that the vehicle 100 is understeering or oversteering, thereby prompting the driver to take measures such as corrective steering.

[0051] Figure 2 is a functional block diagram showing the process of vehicle behavior estimation in the MCU 510 .

[0052] Figure 2The functional block diagram is roughly divided into a first module (block) 700 that outputs a yaw rate deviation Dγ [deg / s] as a first deviation, a second module 800 that outputs an axial force deviation DAF [kN] as a second deviation, and a third module 900 that compares the output of the first module 700 with the output of the second module 800 and outputs an understeer or oversteer detection signal as a control signal to turn the vehicle behavior notification on and off.

[0053] Here, the first module 700 for obtaining the yaw rate deviation Dγ obtains the deviation between the standard yaw rate γn and the actual yaw rate γa, that is, the yaw rate deviation Dγ, and compares the yaw rate deviation Dγ with a threshold value Dγth, thereby outputting a binary signal indicating whether the vehicle 100 is understeering or oversteering.

[0054] On the other hand, the second module 800 for calculating the axial force deviation DAF calculates the deviation between the standard axial force AFn [kN] of the rack rod 421 and the estimated axial force AFe [kN], i.e., the axial force deviation DAF [kN], and compares the axial force deviation DAF with the threshold value THaf, thereby outputting a binary signal indicating whether interference affecting the yaw rate deviation Dγ is generated.

[0055] The disturbance that affects the yaw rate deviation Dγ is, for example, the state of the road surface on which the vehicle 100 is traveling, more specifically, the unevenness of the road surface.

[0056] Furthermore, the third module 900 performs a logic operation on the binary signal output by the first module 700 and the binary signal output by the second module 800 to output a binary signal indicating whether understeering or oversteering occurs.

[0057] The detection of understeering or oversteering based on the yaw rate deviation Dγ in the first module 700 may cause erroneous detection due to the yaw rate deviation Dγ generated by disturbances such as unevenness of the road surface.

[0058] Therefore, the third module 900 compares the understeering or oversteering detection result in the first module 700 with the interference detection result in the second module 800, and performs final understeering or oversteering detection, thereby suppressing erroneous detection caused by interference.

[0059] Hereinafter, the detailed structures of the first module 700, the second module 800, and the third module 900 will be described.

[0060] The first module 700 includes a first coefficient setting unit 701 , a standard yaw rate setting unit 702 , a phase control unit 703 , a second coefficient setting unit 704 , a third coefficient setting unit 705 , a first multiplication unit 706 , a second multiplication unit 707 , a deviation calculation unit 708 , and a comparison unit 709 .

[0061] The first coefficient setting unit 701 acquires a signal of the vehicle speed VS, and sets a time coefficient Tf that is a characteristic value of a response delay of the vehicle behavior with respect to steering based on the vehicle speed VS.

[0062] The standard yaw rate setting unit 702 acquires a signal of the vehicle speed VS and a signal of a target rack stroke RStg (in other words, a target steering angle) as steering operation information, and obtains a basic standard yaw rate γnb which is a basic value of the standard yaw rate γn based on these signals.

[0063] In other words, the standard yaw rate setting unit 702 obtains a basic standard yaw rate γnb as a standard traveling state of the vehicle 100 based on the steering operation information and the first physical quantity related to the traveling speed of the vehicle 100 .

[0064] Furthermore, the standard yaw rate setting unit 702 can obtain the basic standard yaw rate γnb based on the vehicle speed VS and the operation angle θ of the steering wheel 310 as steering operation information.

[0065] The phase control unit 703 obtains the signal of the time coefficient Tf set by the first coefficient setting unit 701 and the signal of the basic standard yaw rate γnb obtained by the standard yaw rate setting unit 702 , and delays the phase of the basic standard yaw rate γnb according to the time coefficient Tf.

[0066] The second coefficient setting unit 704 obtains the longitudinal acceleration [m / s 2 ] signal, and sets a variation coefficient DC corresponding to the variation characteristics of the yaw rate γ when the vehicle 100 is decelerated.

[0067] Furthermore, the third coefficient setting unit 705 acquires a signal of the longitudinal acceleration [m / s 2 ] of the vehicle 100 detected by the longitudinal acceleration sensor 630 , and sets a variation coefficient AC corresponding to the variation characteristics of the yaw rate γ when the vehicle 100 is accelerated.

[0068] Then, the first multiplication unit 706 obtains the signal of the basic standard yaw rate γnb after phase control output by the phase control unit 703, and the change coefficient DC during deceleration set by the second coefficient setting unit 704, multiplies the basic standard yaw rate γnb by the change coefficient DC during deceleration, and outputs the multiplication result as the basic standard yaw rate γnb after correction during deceleration.

[0069] Furthermore, the second multiplication unit 707 obtains the signal of the basic standard yaw rate γnb corrected during deceleration output by the first multiplication unit 706, and the variation coefficient AC during acceleration set by the third coefficient setting unit 705, multiplies the basic standard yaw rate γnb corrected during deceleration by the variation coefficient AC during acceleration, and outputs the multiplication result as the standard yaw rate γn.

[0070] The deviation calculation unit 708 obtains the signal of the standard yaw rate γn outputted from the second multiplication unit 707 and the signal of the actual yaw rate γac detected by the yaw rate sensor 640 , and outputs the result of subtracting the actual yaw rate γac from the standard yaw rate γn as a signal of yaw rate deviation Dγ (Dγ=γn−γac).

[0071] Here, the standard yaw rate γn is a standard running state obtained based on the steering operation information, and the actual yaw rate γac detected by the yaw rate sensor 640 is a running state actually occurring in the vehicle 100 .

[0072] Therefore, the deviation calculation unit 708 is a functional unit that compares the standard driving state with the actual driving state and outputs the first deviation.

[0073] The comparison unit 709 obtains the signal of the yaw rate deviation Dγ and the signal of the threshold value Dγth obtained by the deviation calculation unit 708 , compares the yaw rate deviation Dγ with the threshold value Dγth, and outputs a binary signal indicating whether the vehicle is in an understeering or oversteering state.

[0074] Here, the state in which the output signal of the comparison unit 709 is 1 (High) indicates that understeering or oversteering is detected.

[0075] On the other hand, a state where the output signal of the comparison unit 709 is 0 (Low) indicates that understeering or oversteering is not detected, in other words, a natural steering state in which the standard yaw rate γn and the actual yaw rate γac are close.

[0076] The yaw rate deviation Dγ is calculated as a positive or negative value, and the threshold value Dγth is also set to a positive first threshold value Dγth1 and a negative second threshold value Dγth2 .

[0077] Furthermore, when the yaw rate deviation Dγ is within a region sandwiched between the first threshold value Dγth1 and the second threshold value Dγth2 (Dγth1 ≥ Dγ ≥ Dγth2 ), the comparison unit 709 sets the output signal to 0 (Low).

[0078] Furthermore, the comparison unit 709 sets the output signal to 1 (High) when the yaw rate deviation Dγ is larger than the first threshold value Dγth1 (Dγth1<Dγ), and also sets the output signal to 1 (High) when the yaw rate deviation Dγ is smaller than the second threshold value Dγth2 (Dγth2>Dγ).

[0079] In other words, when the absolute value of the yaw rate deviation Dγ is larger than the positive threshold value, the comparison unit 709 sets the output signal to 1 (High).

[0080] Figure 3 The upper part of exemplifies the correlation between the yaw rate deviation Dγ and the threshold values ​​Dγth1 and Dγth2.

[0081] Figure 3 The yaw rate deviation Dγ is in a state of periodic fluctuations due to the unevenness of the road surface, and periodically repeats a state in which the yaw rate deviation Dγ is greater than a first threshold value Dγth1, a state in which the yaw rate deviation Dγ is within a region sandwiched between the first threshold value Dγth1 and the second threshold value Dγth2, and a state in which the yaw rate deviation Dγ is less than the second threshold value Dγth2.

[0082] At this time, the output signal of the comparison unit 709 switches alternately between 1 (High) and 0 (Low).

[0083] As described above, the first module 700 compares the standard yaw rate γn obtained based on the rack stroke and vehicle speed as steering operation information with the yaw rate actually generated in the vehicle 100, calculates the yaw rate deviation Dγ, and determines whether the vehicle 100 is understeering or oversteering based on the yaw rate deviation Dγ.

[0084] On the other hand, the second module 800 includes a standard axial force calculation module 810 , an estimated axial force calculation module 820 , a deviation calculation unit 830 and a comparison unit 840 .

[0085] The standard axial force calculation module 810 includes a basic standard axial force setting unit 811 , a rack stroke speed calculation unit 812 , a standard axial force intercept calculation unit 813 , and an adding unit 814 .

[0086] The basic standard axial force setting unit 811 obtains a signal of the rack stroke RS and a signal of the vehicle speed VS, and obtains a basic standard axial force AFnb which is a basic value of the standard axial force AFn generated in the rack bar 421 based on these signals.

[0087] The rack stroke speed calculation unit 812 differentiates the signal of the rack stroke RS to obtain the rack stroke speed ΔRS [mm / s] which is the amount of change in the rack stroke per unit time.

[0088] The standard axial force intercept calculation unit 813 obtains a signal of the rack stroke speed ΔRS and a signal of the vehicle speed VS, and obtains an intercept ΔAF as a correction value for correcting the basic standard axial force AFnb.

[0089] Then, the adding unit 814 obtains the signal of the basic standard axial force AFnb and the signal of the intercept ΔAF, adds the intercept ΔAF to the basic standard axial force AFnb, and outputs the result as the final standard axial force AFn (AFn=AFnb+ΔAF).

[0090] In this way, the standard axial force calculation module 810 obtains the standard axial force AFn generated in the rack bar 421 based on the first physical quantity related to the driving speed of the vehicle 100 and the second physical quantity related to the steering angle of the front wheels 101 and 102 .

[0091] The estimated axial force calculation module 820 includes a friction compensation unit 821 , a friction compensation subtraction unit 822 , an axial force conversion unit 823 , a motor inertia compensation unit 824 , and an estimated axial force correction unit 825 .

[0092] The friction compensating unit 821 acquires a signal of the motor rotation speed MRS [rpm] of the steering motor 410 , and obtains a current value CMF [Arms] of the mechanical friction amount based on the motor rotation speed MRS.

[0093] The motor rotation speed MRS is obtained based on the rotation angle θm [deg] of the steering motor 410 detected by the motor rotation angle sensor 440 .

[0094] The friction compensation subtraction unit 822 obtains the signal of the motor current value Cm detected by the motor current sensor 450 and the signal of the current value CMF of the mechanical friction amount calculated by the friction compensation unit 821, subtracts the current value CMF of the mechanical friction amount from the motor current value Cm, and outputs the motor current value Cm with the mechanical friction amount corrected.

[0095] The axial force conversion unit 823 acquires the signal of the motor current value Cm output from the friction compensation subtraction unit 822 , and obtains the basic estimated axial force AFeb estimated to be generated in the rack bar 421 based on the acquired motor current value Cm.

[0096] The conversion characteristics for obtaining the basic estimated axial force AFeb from the motor current value Cm are determined by the rated torque, rated current, reduction ratio of the steering motor 410 , and the stroke ratio (rack gain) in the steering device 400 .

[0097] The motor inertia compensating unit 824 acquires a signal of the motor rotation speed MRS of the steering motor 410 , and obtains the axial force AFJ [kN] of the inertia (moment of inertia) of the steering motor 410 based on the motor rotation speed MRS.

[0098] The estimated axial force correction unit 825 obtains the signal of the basic estimated axial force AFeb calculated by the axial force conversion unit 823 and the axial force AFJ of the inertia calculated by the motor inertia compensation unit 824, and subtracts the axial force AFJ of the inertia from the basic estimated axial force AFeb, and outputs the final estimated axial force AFe (AFe=AFeb-AFJ).

[0099] As described above, the estimated axial force calculation module 820 obtains the estimated axial force AFe based on the third physical quantity related to the motor current value Cm of the steering motor 410 and the fourth physical quantity related to the motor rotation speed MRS of the steering motor 410 .

[0100] Then, the deviation calculation unit 830 obtains the signal of the standard axial force AFn output by the addition unit 814 and the signal of the estimated axial force AFe output by the estimated axial force correction unit 825, and outputs the result of subtracting the estimated axial force AFe from the standard axial force AFn as a signal of the axial force deviation DAF (DAF=AFn-AFe).

[0101] The comparison unit 840 obtains the signal of the axial force deviation DAF and the signal of the threshold value THaf obtained by the deviation calculation unit 830, and outputs a binary signal indicating the presence or absence of disturbance such as unevenness of the road surface based on the comparison between the axial force deviation DAF and the threshold value THaf.

[0102] That is, the comparison unit 840 sets a predetermined threshold value for the axial force deviation DAF and compares the axial force deviation DAF with the predetermined threshold value, thereby distinguishing the presence or absence of disturbance such as unevenness of the road surface.

[0103] Figure 3 The graph shows changes in the yaw rate deviation Dγ and the axial force deviation DAF when the vehicle 100 travels on a rough road surface.

[0104] The axial force deviation DAF is affected by the unevenness of the road surface and fluctuates periodically. The yaw rate deviation Dγ is also affected by the unevenness of the road surface and fluctuates periodically.

[0105] Specifically, when there is unevenness on the road surface, the vehicle body vibrates vertically, and the yaw rate sensor 640 erroneously detects the actual yaw rate γa, thereby generating a yaw rate deviation Dγ.

[0106] Then, the yaw rate deviation Dγ exceeds the threshold value Dγth (the first threshold value Dγth1 and the second threshold value Dγth2 ) and changes, and thus the first module 700 erroneously detects understeering or oversteering.

[0107] Therefore, in order to distinguish the change in the yaw rate deviation Dγ affected by the disturbance and the change in the yaw rate deviation Dγ caused by understeering or oversteering, the second module 800 determines the presence or absence of disturbance such as unevenness of the road surface based on the comparison between the axial force deviation DAF and the threshold value THaf.

[0108] Here, when the axial force deviation DAF and the yaw rate deviation Dγ vary due to the unevenness of the road surface, the axial force deviation DAF has a characteristic of having a higher frequency of variation than the yaw rate deviation Dγ.

[0109] Therefore, the comparison unit 840 sets the frequency threshold value THFaf for determining whether the frequency of variation of the axial force deviation DAF is higher than the frequency of variation of the yaw rate deviation Dγ, based on the frequency of variation of the yaw rate deviation Dγ.

[0110] Furthermore, when the frequency of the axial force deviation DAF is higher than the frequency threshold THFaf, in other words, when the frequency of the axial force deviation DAF is higher than the frequency of the yaw rate deviation Dγ, the comparison unit 840 determines that the axial force deviation DAF varies due to the unevenness of the road surface, and sets the output signal to 0 (Low).

[0111] That is, when the output signal of the comparison unit 840 is 0 (Low), it means that the unevenness of the road surface as disturbance is detected, in other words, it means that the yaw rate deviation Dγ varies due to the unevenness of the road surface.

[0112] On the other hand, when the frequency of the axial force deviation DAF is equal to or smaller than the frequency threshold THFaf, the comparison unit 840 determines that there is no unevenness in the road surface that affects the yaw rate deviation Dγ, and sets the output signal to 1 (High).

[0113] That is, the output signal of the comparison unit 840 being 1 (High) indicates that the unevenness of the road surface as disturbance is not detected, in other words, that the yaw rate deviation Dγ is not affected by the disturbance and changes due to the behavior of the vehicle 100 , that is, understeering or oversteering.

[0114] In addition, the comparison unit 840 can set an amplitude threshold THAaf for determining the amplitude of the axial force deviation DAF, and when the amplitude of the axial force deviation DAF exceeds the amplitude threshold THAaf, the output signal is set to 0 (Low), and when the amplitude of the axial force deviation DAF is below the amplitude threshold THAaf, the output signal is set to 1 (High).

[0115] That is, the comparison unit 840 can determine the presence or absence of the unevenness of the road surface as disturbance by comparing the amplitude of the axial force deviation DAF with the amplitude threshold value THAaf.

[0116] Furthermore, the comparison unit 840 can determine the presence or absence of unevenness of the road surface as disturbance by comparing the amplitude of the axial force deviation DAF with the amplitude threshold THAaf and comparing the frequency of the axial force deviation DAF with the frequency threshold THFaf.

[0117] In this case, when the amplitude of the axial force deviation DAF exceeds the amplitude threshold THAaf and the frequency of the axial force deviation DAF is higher than the frequency threshold THFaf, the comparison unit 840 determines that the axial force deviation DAF varies due to the unevenness of the road surface and sets the output signal to 0 (Low).

[0118] Furthermore, when at least one of the conditions that the amplitude of the axial force deviation DAF is less than the amplitude threshold THAaf and the frequency of the axial force deviation DAF is less than the frequency threshold THFaf is satisfied, the comparison unit 840 determines that there is no unevenness in the road surface and sets the output signal to 1 (High).

[0119] As described above, the comparison unit 840 (second module 800 ) determines the presence or absence of the unevenness of the road surface as a disturbance based on the amplitude and / or frequency of the axial force deviation DAF.

[0120] The third module 900 includes a logical AND operation unit 910 .

[0121] The logical AND operation unit 910 inputs the binary signal output by the comparison unit 709 of the first module 700 and the binary signal output by the comparison unit 840 of the second module 800, performs a logical AND operation on these signals, and outputs a binary signal as the operation result.

[0122] As described above, the comparison unit 709 sets the output signal to 1 (High) when understeering or oversteering is detected based on the yaw rate deviation Dγ.

[0123] On the other hand, when the comparison unit 840 determines that the axial force deviation DAF varies due to the unevenness of the road surface (in other words, the unevenness of the road surface as disturbance occurs) based on the comparison between the axial force deviation DAF and the threshold value THaf, the output signal is set to 0 (Low).

[0124] At this time, the output signal of the logical AND operation unit 910 becomes 0 (Low).

[0125] That is, even if the comparison unit 709 detects understeer or oversteer based on the yaw rate deviation Dγ, when the comparison unit 840 detects unevenness of the road surface as disturbance, the output signal of the logical AND operation unit 910 becomes 0 (Low) indicating that understeer or oversteer is not detected.

[0126] In other words, when the comparison unit 840 detects the unevenness of the road surface as disturbance, the yaw rate deviation Dγ is considered to be caused by the disturbance, and the detection result of understeering or oversteering is ultimately invalidated.

[0127] On the other hand, when the comparison unit 709 detects understeer or oversteer based on the yaw rate deviation Dγ and the output signal of the comparison unit 709 is 1 (High), and when the comparison unit 840 does not detect the unevenness of the road surface and the output signal of the comparison unit 840 is 1 (High), the output signal of the logical AND operation unit 910 becomes 1 (High).

[0128] That is, when understeering or oversteering is detected based on the yaw rate deviation Dγ and the unevenness of the road surface is not detected, the output signal of the logical AND operation unit 910 becomes 1 (High) indicating that understeering or oversteering is detected.

[0129] In other words, when the unevenness of the road surface serving as disturbance is not detected, the MCU 510 determines the presence or absence of understeering or oversteering based on the yaw rate deviation Dγ.

[0130] Therefore, according to the vehicle behavior estimation method executed by the MCU 510, when the yaw rate deviation Dγ is generated due to the influence of the unevenness of the road surface, erroneous detection of understeering or oversteering is suppressed, and the detection accuracy of understeering or oversteering is improved.

[0131] The MCU 510 supplies the output signal of the logical AND operation unit 910 indicating whether understeering or oversteering is detected (in other words, an understeering / oversteering detection signal) as an on / off control signal to the warning lamp 650 as a warning device.

[0132] The warning lamp 650 lights up when the output signal of the logical AND operation unit 910 is 1 (High), and notifies the driver of the vehicle 100 of the occurrence of understeering or oversteering.

[0133] In other words, when the MCU 510 estimates the occurrence of understeering or oversteering, it activates the warning lamp 650 which is a warning device provided in the vehicle 100 .

[0134] By lighting the warning lamp 650 , the driver of the vehicle 100 can recognize the occurrence of understeering or oversteering and can perform an operation to cope with the understeering or oversteering, for example.

[0135] Here, the MCU 510 can suppress the occurrence of erroneous detection of understeering or oversteering due to the influence of the unevenness of the road surface, and thus can transmit accurate information on understeering or oversteering to the driver of the vehicle 100 .

[0136] The technical concepts described in the above embodiments can be used in combination as appropriate unless there is any contradiction.

[0137] Furthermore, although the contents of the present invention have been specifically described with reference to the preferred embodiments, it is obvious that those skilled in the art can adopt various modified forms based on the basic technical ideas and teachings of the present invention.

[0138] For example, the comparison unit 709 can distinguish and detect vehicle behavior as oversteering and understeering by determining whether the yaw rate deviation Dγ exceeds a first threshold value Dγth1 and further determining whether the yaw rate deviation Dγ is lower than a second threshold value Dγth2.

[0139] Furthermore, the comparison unit 840 can be configured to invalidate the detection result of oversteering or understeering when the unevenness of the road surface is detected as disturbance.

[0140] Furthermore, when the MCU 510 detects oversteering and understeering, it is possible to operate the warning device in such a manner that the driver can distinguish between oversteering and understeering.

[0141] Furthermore, when the MCU 510 detects oversteering and understeering by distinguishing between them, it is possible to reflect the detection result in the steering control and automatically perform corrective steering for oversteering or understeering.

[0142] The warning device for notifying the driver of the vehicle 100 of the occurrence of oversteering or understeering is not limited to the warning lamp 650. For example, as the warning device, a warning buzzer, a liquid crystal display device, a voice guidance device, etc. can be used.

[0143] Furthermore, the steer-by-wire steering system 200 may include a backup mechanism that mechanically couples the steering wheel 310 and the front wheels 101 , 102 via a clutch or the like.

[0144] Furthermore, the steer-by-wire steering system 200 may include a first control device that outputs a control signal for the steering motor 410 and a second control device that outputs a control signal for the reaction force motor 330 , respectively.

[0145] In the steering system 200 , any one of the first control device and the second control device can include a control unit that executes the vehicle behavior detection method, and function as a vehicle behavior detection device.

[0146] Furthermore, an electronic control device that does not have a control function of the steering system 200 (in other words, the reaction force motor 330 and the steering motor 410 ) can include a control unit that executes the vehicle behavior detection method and function as a vehicle behavior detection device.

[0147] Description of Reference Numerals

[0148] 100…Vehicle; 101, 102…Front wheels; 200…Steering system; 300…Steering operation input device; 340…Operation angle sensor; 400…Steering device; 410…Steering motor; 421…Rack rod (movable component); 430…Rack stroke sensor; 500…Steering control device (vehicle behavior detection device); 510…Microcomputer (control unit).

Claims

1. A vehicle behavior estimation method, the method being executed by a control unit mounted on a vehicle, the vehicle comprising a motor for applying a steering torque to wheels of the vehicle via a movable member, wherein: The control unit: deriving a standard driving state of the vehicle based on the steering operation information of the driver of the vehicle; Compare the standard driving state with the driving state actually generated on the vehicle and output a first deviation; Calculating a standard axial force generated in the movable member based on a first physical quantity related to the running speed of the vehicle and a second physical quantity related to the steering angle of the wheel; Calculating an estimated axial force generated in the movable member based on a third physical quantity related to a current value of the motor; comparing the standard axial force with the estimated axial force and outputting a second deviation; as well as The behavior of the vehicle is estimated by comparing the first deviation to the second deviation.

2. The vehicle behavior estimation method according to claim 1, wherein: The control unit obtains an estimated axial force generated in the movable member based on the third physical quantity and a fourth physical quantity related to the rotation speed of the motor.

3. The vehicle behavior estimation method according to claim 1, wherein: The control unit: determining a standard yaw rate as the standard driving state based on the steering operation information and the first physical quantity; and The standard yaw rate is compared with a yaw rate actually occurring in the vehicle, and the first deviation is output.

4. The vehicle behavior estimation method according to claim 3, wherein: The control unit sets a predetermined threshold value for the second deviation.

5. The vehicle behavior estimation method according to claim 4, wherein: The control unit: determining whether the vehicle is understeering or oversteering based on the first deviation; as well as When the second deviation exceeds the predetermined threshold, it is determined that the first deviation is caused by disturbance.

6. The vehicle behavior estimation method according to claim 4, wherein: The control unit determines whether the vehicle is understeering or oversteering based on the first deviation when the second deviation does not exceed the predetermined threshold value.

7. A vehicle behavior detection device, comprising the control unit for executing the vehicle behavior estimation method according to claim 1, wherein: The control unit activates an alarm device provided in the vehicle based on the estimated behavior of the vehicle.

8. A steering system comprising: The vehicle behavior detection device according to claim 7; the movable member; and The motor.

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