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

Abstract

A vehicle behavior estimation method, a vehicle behavior recognition device, and a steering system of the present invention provide, in one aspect, a vehicle including a motor that applies steering torque to road wheels of the vehicle via a movable member, in which a normative driving state of the vehicle calculated from steering operation information of the driver is compared with an actual driving state of the vehicle to output a first deviation, a normative axial force generated in the movable member and calculated from the traveling speed of the vehicle and the steering angle of the road wheels is compared with the estimated axial force generated in the movable member and calculated from the current value of the motor to output a second deviation, and the behavior of the vehicle is estimated by comparing the first deviation with the second deviation.This makes it possible to improve the accuracy of vehicle behavior detection.

Description

TECHNICAL FIELD

[0001] The present invention relates to a vehicle behavior estimation method, a vehicle behavior recognition device, and a steering system. TECHNICAL BACKGROUND

[0002] The vehicle turning behavior control device of Patent Document 1 calculates a target yaw rate based on the steering angle and the vehicle speed, determines that the vehicle is in an understeer state when the actual yaw rate input from the yaw rate sensor is less than the target yaw rate, and determines that the vehicle is in an oversteer state when the actual yaw rate is greater than the target yaw rate. LIST OF REFERENCE DOCUMENTSPATENT DOCUMENT

[0003] Patent Document 1: JP 2011-093489 A SUMMARY OF THE INVENTION TASK TO BE SOLVED BY THE INVENTION

[0004] A yaw rate deviation is the deviation between the normative yaw rate, which is calculated from the steering angle of the road wheels, vehicle speed, etc., and the yaw rate actually occurring in a vehicle. When vehicle behavior is understeer or oversteer, and this behavior is detected based on the yaw rate deviation, the yaw rate deviation also occurs due to disturbances such as an uneven road surface on which the vehicle is traveling.

[0005] It is therefore problematic that the vehicle behavior based on the yaw rate deviation becomes less accurate due to disturbances.

[0006] The present invention has been made in view of the conventional circumstances, and it is an object of the present invention to provide a vehicle behavior estimation method, a vehicle behavior recognition apparatus, and a steering system that can improve accuracy of vehicle behavior recognition. MEANS TO SOLVED THE TASK

[0007] A vehicle behavior estimation method, a vehicle behavior recognition device, and a steering system according to the present invention, in one aspect, calculate a normative driving state of a vehicle from steering operation information of a driver of the vehicle, compare the normative driving state with a driving state actually occurring in the vehicle, and output a first deviation, calculate a normative axial force generated in a movable member from a first physical quantity related to a traveling speed of the vehicle and a second physical quantity related to a steering angle of the road wheels, calculate an estimated axial force generated in the movable member from a third physical quantity related to a current value of a motor, compare the normative 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. EFFECTS OF THE INVENTION

[0008] According to the present invention, it is possible to improve accuracy of vehicle behavior recognition. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic diagram of a vehicle incorporating a steer-by-wire steering system. Fig. 2 is a functional block diagram showing a process for estimating a vehicle behavior. Fig. 3 is a time chart illustrating a change in yaw rate deviation and axial force deviation in an uneven area of ​​a road surface. EMBODIMENT OF THE INVENTION

[0009] Hereinafter, an embodiment of a vehicle behavior estimation method, a vehicle behavior recognition apparatus, and a steering system according to the present invention will be described based on the drawings.

[0010] Fig. 1 is a schematic diagram showing an example of a vehicle 100 in which a steer-by-wire steering system 200 is mounted.

[0011] Vehicle 100 is a four-wheeled automobile having a pair of road wheels, one of which is a right front road wheel 101 and the other of which is a left front road wheel 102, and a pair of road wheels, one of which is a right rear road wheel 103 and the other of which is a left rear road wheel 104.

[0012] Steering system 200 includes a steering operation input device 300 to which the steering operation of the driver of vehicle 100 is input via a steering wheel 310, a steering device 400 having a steering motor 410 that applies steering torque to the road wheels (specifically, front road wheels 101 and 102) of vehicle 100, and a steering control device 500.

[0013] Here, the operating input device 300 and the steering device 400 are mechanically separated from each other.

[0014] Steering operation input device 300 includes steering wheel 310, a steering shaft 320, a counterforce motor 330, and an operation angle sensor 340.

[0015] Steering wheel 310 is a steering input element operated by the driver of vehicle 100.

[0016] Counterforce motor 330 is an actuator to apply a simulated steering counterforce torque to steering wheel 310.

[0017] Operating angle sensor 340 is a sensor that detects an operating angle θ [deg] of steering wheel 310.

[0018] Steering device 400 includes a steering mechanism 420.

[0019] Steering mechanism 420 changes steering angles of front road wheels 101 and 102 by converting the rotational movement of steering motor 410 into a linear movement of a rack 421 based on a rack and pinion drive mechanism.

[0020] That is, steering motor 410 applies steering torque to front road wheels 101 and 102 via rack 421, which is a movable member.

[0021] In addition, steering device 400 includes a rack stroke sensor 430 for detecting a rack stroke RS [mm], which is the stroke amount of rack 421 that correlates with the steering angle of front road wheels 101 and 102, a motor rotation angle sensor 440 for detecting a rotation angle θm [deg] of steering motor 410, and a motor current sensor 450 for detecting a current value Cm [Arms] of steering motor 410.

[0022] Steering control device 500 is an electronic control device that includes an MCU (Micro Control Unit) 510 and controls the operation of steering system 200 by controlling counterforce motor 330 and steering motor 410, which are the actuators included in steering system 200.

[0023] In other words, MCU 510 may be referred to as a microcomputer, a processor, a processing device, an arithmetic device, or the like.

[0024] MCU 510 performs arithmetic processing on various types of signals acquired from the outside to calculate a control signal for counterforce motor 330 and a control signal for steering motor 410, and outputs these calculated control signals.

[0025] Here, steering control device 500 may include a pre-driver, an inverter, etc., for controlling the current flowing through counterforce motor 330 and the current flowing through steering motor 410.

[0026] Separate from steering control device 500, vehicle 100 may include a system including a drive circuit including a pre-driver, an inverter, etc.

[0027] Vehicle 100 also includes wheel speed sensors 621 to 624 for detecting wheel speeds WS1 to WS4, which are rotational speeds of road wheels 101 to 104, a longitudinal acceleration sensor 630 for detecting longitudinal acceleration G of vehicle 100, and a yaw rate sensor 640 for detecting a yaw rate γ [deg / s] occurring in vehicle 100.

[0028] MCU 510 of steering control device 500 detects output signals from operating angle sensor 340, steering rod stroke sensor 430, motor rotation angle sensor 440, motor current sensor 450, wheel speed sensors 621 to 624, longitudinal acceleration sensor 630, and yaw rate sensor 640.

[0029] Here, the control details of steering system 200 (specifically, counterforce motor 330 and steering motor 410) by MCU 510 of steering control device 500 are briefly described.

[0030] 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 rack 421, based on information about operating angle θ of steering wheel 310.

[0031] MCU 510 then calculates a control signal of steering motor 410 based on the deviation between actual rack stroke RS detected by rack stroke sensor 430 and target rack stroke RStg, in other words, based on the control error of the steering angle, and outputs the calculated control signal to the drive circuit of steering motor 410.

[0032] Although actual rack stroke RS is detected using rack stroke sensor 430 in this embodiment, actual rack stroke RS, which is the stroke amount of rack 421, may also be calculated from a motor rotation angle θm detected by motor rotation angle sensor 440, etc.

[0033] Actual rack stroke RS can be calculated using the detector provided on the rack gear, which detects the rotation angle of the gear shaft.

[0034] In addition, MCU 510 calculates a reaction torque command value TRtg, which is the target value of a reaction torque TR, based on the vehicle speed VS [km / h] calculated from wheel speeds WS1 to WS4 and the information on operating angle θ of steering wheel 310.

[0035] MCU 510 can calculate vehicle speed VS by detecting wheel speed signals WS1 to WS4 from wheel speed sensors 621 to 624. MCU can acquire information about vehicle speed VS calculated by another electronic control device based on the wheel speed signals WS1 to WS4 via an on-board network.

[0036] Next, MCU 510 outputs a control signal based on counterforce torque command value TRtg to the drive circuit of counterforce motor 330.

[0037] In this manner, MCU 510 controls the operation of steering system 200 by controlling the steering torque applied to front road wheels 101 and 102 and by controlling reaction torque applied to steering wheel 310.

[0038] In addition, MCU 510 has a function of estimating the vehicle behavior according to a predetermined procedure and providing a vehicle behavior notification for notifying the driver of the vehicle 100 of the estimated vehicle behavior.

[0039] That is, MCU 510 is a control unit that executes the vehicle behavior estimation process and constitutes the vehicle behavior recognition device.

[0040] Here the vehicle behavior is understeer (U / S) or oversteer (O / S), which is the cornering behavior of vehicle 100.

[0041] It is difficult for the driver to detect understeer or oversteer because the steering force from steering wheel 310 does not change in the steer-by-wire steering system 200 even when vehicle 100 understeers or oversteers.

[0042] Thus, MCU 510 estimates whether or not vehicle 100 is understeering or oversteering, and warns the driver when vehicle 100 is understeering or oversteering, so that the driver is prompted to take actions such as performing corrective steering.

[0043] Fig. 2 is a functional block diagram showing a process for estimating vehicle behavior in MCU 510.

[0044] The functional block diagram of Fig. 2 is roughly divided into a first block 700 for outputting a yaw rate deviation Dγ [deg / s] as the first deviation, a second block 800 for outputting an axial force deviation DAF [kN] as the second deviation, and a third block 900 for comparing the output of the first block 700 with the output of the second block 800 and outputting an understeer or oversteer detection signal as the control signal that turns the vehicle behavior notification ON and OFF.

[0045] Here, first yaw rate deviation Dγ calculation block 700 calculates yaw rate deviation Dγ, which is the deviation between a normative yaw rate γn and an actual yaw rate γa, and compares yaw rate deviation Dγ with a threshold value Dγth to output a binary signal indicating whether vehicle 100 is understeering or oversteering.

[0046] On the other hand, second block for calculating axial force deviation DAF calculates the axial force deviation DAF [kN], which is the deviation between a normative axial force AFn [kN] and an estimated axial force AFe [kN] of rack 421, and compares axial force deviation DAF with a threshold value THaf to output a binary signal indicating whether a disturbance affecting yaw rate deviation Dγ has occurred or not.

[0047] For example, a disturbance that affects yaw rate deviation Dγ is the condition of the road surface on which vehicle 100 is traveling, and specifically an uneven road surface.

[0048] Third block 900 performs a logical operation on the binary signal output from first block 700 and the binary signal output from second block 800 to output a binary signal indicating whether or not understeer or oversteer has occurred.

[0049] The detection of understeer or oversteer based on a yaw rate deviation Dγ in first block 700 may result in erroneous detection if yaw rate deviation Dγ occurs due to a disturbance such as an uneven road surface.

[0050] Thus, third block 900 compares the detection result of understeer or oversteer in first block 700 with the detection result of disturbance in second block 800, and performs the final detection of understeer or oversteer to avoid erroneous detection due to disturbance.

[0051] The detailed configuration of each of the first block 700, second block 800, and third block 900 is described below.

[0052] First block 700 includes a first coefficient setting unit 70, a normative 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 arithmetic unit 708, and a comparison unit 709.

[0053] First coefficient setting unit 701 detects a signal of vehicle speed VS, and sets, based on vehicle speed VS, a time coefficient Tf which is the characteristic value of the response delay of the vehicle behavior with respect to steering.

[0054] Normative yaw rate setting unit 702 acquires the signal of vehicle speed VS and a signal of target rack stroke RStg (in other words, the target steering angle) as the steering operation information, and calculates a basic normative yaw rate γnb, which is the basic value of normative yaw rate γn, based on them.

[0055] In other words, normative yaw rate setting unit 702 calculates basic normative yaw rate γnb as the normative driving state of vehicle 100 from the steering operation information and the first physical quantity related to the driving speed of vehicle 100.

[0056] Normative yaw rate setting unit 702 may calculate basic normative yaw rate γnb based on vehicle speed VS and operating angle γ of steering wheel 310 as the steering operating information.

[0057] Phase control unit 703 detects the signal of time coefficient Tf set by first coefficient setting unit 701 and the signal of basic normative yaw rate γnb calculated by normative yaw rate setting unit 702, and delays the phase of basic normative yaw rate γnb according to time coefficient Tf.

[0058] Second coefficient setting unit 704 detects a signal of a longitudinal acceleration [m / s 2 ] of vehicle 100 detected by longitudinal acceleration sensor 630, and sets a change coefficient DC according to the change characteristic of yaw rate γ when vehicle 100 decelerates.

[0059] In addition, the third coefficient setting unit 705 detects a signal of longitudinal acceleration [m / s 2] of vehicle 100 detected by longitudinal acceleration sensor 630, and sets a change coefficient AC according to the change characteristic of yaw rate γ when vehicle 100 accelerates.

[0060] Then, the first multiplication unit 706 acquires the signal of the basic normative yaw rate γnb after phase control, which is output from the phase control unit 703, and the change coefficient DC during deceleration, which is set by the second coefficient setting unit 704. The first multiplication unit 706 then multiplies the basic normative yaw rate γnb by the change coefficient DC during deceleration, and outputs the multiplication result as the basic normative yaw rate γnb corrected during deceleration.

[0061] Further, the second multiplication unit 707 acquires the signal of the basic normative yaw rate γnb corrected during deceleration, which is output by the first multiplication unit 706, and the change coefficient AC during acceleration, which is set by the third coefficient setting unit 705. The second multiplication unit 707 then multiplies the basic normative yaw rate γnb corrected during deceleration by the change coefficient AC during acceleration, and outputs the multiplication result as the normative yaw rate γn.

[0062] Deviation arithmetic unit 708 acquires the normative yaw rate signal γn output from second multiplication unit 707 and the actual yaw rate signal γac detected by yaw rate sensor 640. Deviation arithmetic unit 708 then outputs the result of subtracting the actual yaw rate γac from the normative yaw rate γn as a yaw rate deviation signal Dy (Dγ = γn - γac).

[0063] Here, normative yaw rate γn is the normative driving state calculated based on the steering operation information, and actual yaw rate γac detected by yaw rate sensor 640 is the driving state actually occurring in vehicle 100.

[0064] Thus, deviation arithmetic unit 708 is a functional unit that compares the normative driving state with the actual driving state and outputs the first deviation.

[0065] Comparing unit 709 detects the yaw rate deviation signal Dy calculated by deviation arithmetic unit 708 and the threshold Dγth signal, and compares yaw rate deviation Dγ with threshold Dγth to output a binary signal indicating whether or not the vehicle is in the state of understeer or oversteer.

[0066] Here, the state in which the output signal of comparison unit 709 is 1 (High) indicates that understeer or oversteer has been detected.

[0067] On the other hand, the state in which the output signal of comparison unit 709 is 0 (Low) indicates that understeer or oversteer has not been detected, in other words, the vehicle is in the normal steering state in which normative yaw rate γn and actual yaw rate γac are close to each other.

[0068] Yaw rate deviation Dγ is calculated as a positive or negative value, and a positive first threshold Dγth1 and a negative second threshold Dγth2 are also set for threshold Dγth.

[0069] Then, comparing unit 709 sets the output signal to 0 (Low) when yaw rate deviation Dγ is within the range between first threshold Dγth1 and second threshold Dγth2 (Dγth1 ≥ Dγ ≥ Dγth2).

[0070] In addition, comparison unit 709 sets the output signal to 1 (High) when yaw rate deviation Dγ is greater than first threshold Dγth1 (Dγth1 < Dγ), and also sets the output signal to 1 (High) when yaw rate deviation Dγ is less than second threshold Dγth2 (Dγth2 > Dγ).

[0071] In other words, comparison unit 709 sets the output signal to 1 (High) when the absolute value of yaw rate deviation Dγ is greater than a positive threshold.

[0072] The upper part of Fig. Figure 3 illustrates the correlation between yaw rate deviation Dγ and threshold values ​​Dγth1, Dγth2.

[0073] Yaw rate deviation Dγ in Fig. 3 is in a periodically changing state due to the effects of an uneven road surface, and periodically repeats the state in which yaw rate deviation Dγ is greater than first threshold Dγth1, the state in which yaw rate deviation Dγ is within the range between first threshold Dγth1 and second threshold Dγth2, and the state in which yaw rate deviation Dγ is less than second threshold Dγth2.

[0074] At this time, the output signal of comparison unit 709 changes between 1 (high) and 0 (low).

[0075] As described above, first block 700 calculates yaw rate deviation Dγ by comparing normative yaw rate γn calculated from the vehicle speed and the rack stroke as the steering operation information with the yaw rate actually occurring in vehicle 100, and determines whether or not vehicle 100 is understeering or oversteering based on yaw rate deviation Dγ.

[0076] On the other hand, second block 800 includes a normative axial force calculation block 810, an estimated axial force calculation block 820, a deviation arithmetic unit 830, and a comparison unit 840.

[0077] Normative axial force calculation unit 810 includes a basic normative axial force setting unit 811, a rack stroke speed arithmetic unit 812, a normative axial force intersection arithmetic unit 813, and an addition unit 814.

[0078] Basic normative axial force setting unit 811 detects a rack stroke signal RS and a vehicle speed signal VS, and calculates, based on these signals, a basic normative axial force AFnb, which is a basic value of normative axial force AFn generated in rack 421.

[0079] Rack stroke speed arithmetic unit 812 calculates a rack stroke speed ΔRS [mm / s], which is the amount of change of the rack stroke per unit time, by taking the differential of the rack stroke RS signal.

[0080] Normative axial force intersection arithmetic unit 813 detects a signal of rack stroke speed ΔRS and a signal of vehicle speed VS, and calculates an intersection ΔAF as a correction value for correcting basic normative axial force AFnb.

[0081] Then, addition unit 814 acquires a signal of basic normative axial force AFnb and a signal of intersection ΔAF, adds intersection ΔAF with basic normative axial force AFnb, and outputs the addition result as the final normative axial force AFn (AFn = AFnb + ΔAF).

[0082] In this way, normative axial force calculation block 810 calculates normative axial force AFn generated in rack 421 from the first physical quantity related to the traveling speed of vehicle 100 and the second physical quantity related to the steering angle of front road wheels 101 and 102.

[0083] Estimated axial force calculation block 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.

[0084] Friction compensation unit 821 detects a signal of a motor rotation speed MRS [rpm] from steering motor 410, and calculates a current value CMF [Arms] for the mechanical friction based on motor rotation speed MRS.

[0085] Motor rotation speed MRS is calculated based on rotation angle θm [deg] of steering motor 410, which is detected by motor rotation angle sensor 440.

[0086] Friction compensation subtraction unit 822 detects a signal of a motor current value Cm detected by motor current sensor 450 and a signal of current value CMF for mechanical friction calculated by friction compensation unit 821, subtracts current value CMF for mechanical friction from motor current value Cm, and outputs the subtraction result as motor current value Cm corrected for mechanical friction.

[0087] Axial force conversion unit 823 detects the signal of motor current value Cm output from friction compensation subtraction unit 822 and calculates a basic estimated axial force AFeb estimated to be generated in rack 421 based on the detected motor current value Cm.

[0088] A conversion characteristic for calculating basic estimated axial force AFeb from motor current value Cm is determined, for example, from the rated torque, rated current, and speed reduction ratio of steering motor 410, and the stroke ratio (rack increase) in steering device 400.

[0089] Motor inertia compensation unit 824 detects a signal of motor rotation speed MRS from steering motor 410, and calculates an axial force AFj [kN] for the inertia (moment of inertia) of steering motor 410 based on motor rotation speed MRS.

[0090] Estimated axial force correction unit 825 acquires the signal of estimated axial force AFeb calculated by axial force conversion unit 823 and axial force AFJ for inertia calculated by motor inertia compensation unit 824, subtracts axial force AFJ for inertia from basic axial force AFeb, and outputs final estimated axial force AFe (AFe = AFeb - AFJ).

[0091] As described above, estimated axial force calculation block 820 calculates estimated axial force AFe from the third physical quantity related to motor current value Cm of steering motor 410 and the fourth physical quantity related to motor rotation speed MRS of steering motor 410.

[0092] Then, deviation arithmetic unit 830 acquires the signal of normative axial force AFn output from addition unit 814 and the signal of estimated axial force AFe output from estimated axial force correction unit 825, and outputs the result of subtracting estimated axial force AFe from normative axial force AFn as an axial force deviation signal DAF (DAF = AFn - Afe).

[0093] Comparing unit 840 detects the axial force deviation signal DAF calculated by deviation arithmetic unit 830 and a threshold signal THaf, and outputs, based on a comparison between axial force deviation DAF and threshold THaf, a binary signal indicating whether or not a disturbance such as an uneven road surface is present.

[0094] That is, comparison unit 840 provides a predetermined threshold value for axial force deviation DAF and compares axial force deviation DAF with the predetermined threshold value to discriminate whether a disturbance such as an uneven road surface is present or not.

[0095] Fig. Figure 3 shows how yaw rate deviation Dγ and axial force deviation DAF vary when vehicle 100 is traveling on an uneven road.

[0096] Axial force deviation DAF varies periodically due to the effects of an uneven road surface, and yaw rate deviation Dγ also varies periodically due to the effects of an uneven road surface.

[0097] Specifically, when the road surface is uneven, vertical vibration of the vehicle body occurs, and yaw rate sensor 640 erroneously detects actual yaw rate γa, resulting in the generation of yaw rate deviation Dγ.

[0098] First block 700 incorrectly detects understeer or oversteer when yaw rate deviation Dγ varies outside threshold Dtyh (first threshold Dγth1, second threshold Dγth2).

[0099] Thus, in order to distinguish between the change in yaw rate deviation Dγ due to the effects of a disturbance and the change in yaw rate deviation Dγ due to understeer or oversteer, second block 800 determines whether or not a disturbance such as a rough road is present based on a comparison between axial force deviation DAF and threshold THaf.

[0100] Here, when axial force deviation DAF and yaw rate deviation Dγ vary due to the effects of an uneven road, the variation frequency of axial force deviation DAF will be higher than the variation frequency of yaw rate deviation Dγ.

[0101] Thus, based on the variation frequency of yaw rate deviation Dγ, comparison unit 840 sets a frequency threshold THFaf for determining whether or not the variation frequency of axial force deviation DAF is higher than the variation frequency of yaw rate deviation Dγ.

[0102] When the frequency of axial force deviation DAF is higher than the frequency threshold THFaf, in other words, when the frequency of axial force deviation DAF is higher than the frequency of yaw rate deviation Dγ, comparison unit 840 determines that axial force deviation DAF varies due to an uneven road surface and sets the output signal to 0 (Low).

[0103] That is, the output signal of comparison unit 840 being 0 (Low) indicates that an uneven road surface has been detected as a disturbance, in other words, that yaw rate deviation Dγ varies due to the effects of an uneven road surface.

[0104] On the other hand, when the frequency of axial force deviation DAF is equal to or less than frequency threshold THFaf, comparison unit 840 determines that no uneven road surface that would affect yaw rate deviation Dγ exists and sets the output signal to 1 (High).

[0105] That is, the output signal of comparison unit 840 being equal to 1 indicates that an uneven road surface was not detected as a disturbance, in other words, that yaw rate deviation Dγ varies due to the behavior of vehicle 100, ie, understeer or oversteer, and is not affected by a disturbance.

[0106] Comparing unit 840 may set an amplitude threshold THAaf for determining the amplitude of axial force deviation DAF, set the output signal to 0 (Low) when the amplitude of axial force deviation DAF is outside amplitude threshold THAaf, and set the output signal to 1 (High) when the amplitude of axial force deviation DAF is equal to or less than amplitude threshold THAaf.

[0107] That is, comparison unit 840 can determine whether or not an uneven road exists as a disturbance by comparing the amplitude of axial force deviation DAF with amplitude threshold THAaf.

[0108] Further, comparison unit 840 may determine whether or not an uneven road surface is present as a disturbance by comparing the amplitude of axial force deviation DAF with amplitude threshold THAaf and by comparing the frequency of axial force deviation DAF with frequency threshold THFaf.

[0109] In this case, when the amplitude of axial force deviation DAF is outside an amplitude threshold THAaf and the frequency of axial force deviation DAF is higher than frequency threshold THAaf, comparison unit 840 determines that axial force deviation DAF varies due to an uneven road surface and sets the output signal to 0 (Low).

[0110] If at least one of the conditions that the amplitude of axial force deviation DAF is equal to or less than amplitude threshold THAaf and that the frequency of axial force deviation DAF is equal to or less than frequency threshold THFaf is met, comparison unit 840 determines that no uneven road surface is present and sets the output signal to 1 (High).

[0111] As described above, comparison unit 840 (second block 800) determines whether or not an uneven road surface is present as a disturbance based on the amplitude and / or frequency of axial force deviation DAF.

[0112] Third block 900 contains an AND operation unit 910.

[0113] AND operation unit 910 inputs the binary signal output from comparison unit 709 of first block 700 and the binary signal output from comparison unit 840 of second block, performs an AND operation on these signals, and outputs the binary signal as the operation result.

[0114] As described above, when understeer or oversteer is detected based on yaw rate deviation Dγ, comparison unit 709 sets the output signal to 1 (High).

[0115] On the other hand, when comparing unit 840 determines that axial force deviation DAF varies due to an uneven road surface (in other words, an uneven road surface has occurred as a disturbance), based on the comparison between axial force deviation DAF and threshold value THaf, comparing unit 840 sets the output signal to 0 (Low).

[0116] At this time, the output signal of the AND operation unit 910 becomes 0 (Low).

[0117] That is, even if comparison unit 709 has detected understeer or oversteer based on yaw rate deviation Dγ, if comparison unit 840 has detected an uneven road surface as a disturbance, the output signal of AND operation unit 910 becomes 0 (Low), indicating that understeer or oversteer has not been detected.

[0118] In other words, when comparison unit 840 has detected an uneven road surface as a disturbance, yaw rate deviation Dγ is regarded as being caused by a disturbance, and the detection result of understeer or oversteer is ultimately invalidated.

[0119] On the other hand, at the time when comparison unit 709 has detected understeer or oversteer based on yaw rate deviation Dγ and the output signal of comparison unit 709 is 1 (High), the output signal of AND operation unit 910 becomes 1 (High) when comparison unit 840 has not detected an uneven road surface and the output signal of comparison unit 840 is 1 (High).

[0120] That is, when understeer or oversteer is detected due to yaw rate deviation Dγ and no uneven road surface is detected, the output signal of AND operation unit 910 becomes 1 (High), indicating that understeer or oversteer is detected.

[0121] In other words, if MCU 510 has not detected an uneven road surface as a disturbance, MCU 510 determines whether or not the vehicle is understeering or oversteering based on yaw rate deviation Dγ.

[0122] Thus, according to the vehicle behavior estimation process executed by MCU 510, accuracy of detection of understeer or oversteer is improved by preventing the erroneous detection of understeer or oversteer when yaw rate deviation Dγ has occurred due to the effects of an uneven road surface.

[0123] An output signal from AND operation unit 910 indicating whether understeer or oversteer has been detected (in other words, the understeer or oversteer detection signal) is output from MCU 510 as the ON / OFF control signal to a warning lamp 650 serving as the warning device.

[0124] Warning lamp 650 illuminates when the output signal of AND operation unit 910 is 1 (High) and notifies the driver of vehicle 100 of the occurrence of understeer or oversteer.

[0125] In other words, when MCU 510 estimates the occurrence of understeer or oversteer, MCU 510 activates warning light 650, which is the warning device included in vehicle 100.

[0126] When warning light 650 is illuminated, the driver of vehicle 100 can detect the occurrence of understeer or oversteer and can, for example, take measures to deal with the understeer or oversteer.

[0127] Here, MCU 510 can prevent the erroneous detection of the occurrence of understeer or oversteer due to the effects of an uneven road surface, and thus can provide accurate information regarding understeer or oversteer to the driver of vehicle 100.

[0128] The technical concepts described in the above embodiment may be used in any suitable combination as long as they do not contradict each other.

[0129] Although the present invention has been described above with reference to a preferred embodiment, it will be apparent to those skilled in the art that variations of the embodiment can be made based on the basic technical concept and scope of the present invention.

[0130] For example, comparison unit 790 may recognize oversteer and understeer as different vehicle behaviors by determining whether or not yaw rate deviation Dγ is above first threshold Dγth1 and further determining whether or not yaw rate deviation Dγ is below second threshold Dγth2.

[0131] Furthermore, comparing unit 840 may be configured to invalidate the detection result of understeer or oversteer when comparing unit 840 detects an uneven road surface as a disturbance.

[0132] Further, when MCU 510 detects oversteer and understeer as different vehicle behaviors, MCU 510 may activate a warning device so that the driver can detect oversteer and understeer as different vehicle behaviors.

[0133] Furthermore, when MCU 510 detects oversteer and understeer as different vehicle behaviors, MCU 510 can map the detection result into steering control and automatically perform corrective steering for oversteer or understeer.

[0134] The warning device for notifying the driver of vehicle 100 of the occurrence of oversteer or understeer is not limited to warning lamp 650. For example, a warning buzzer, a liquid crystal display device, an audio guidance device, or the like may be used as the warning device.

[0135] In addition, steer-by-wire steering system 200 may include a backup mechanism that mechanically couples steering wheel 310 to front road wheels 101 and 102 by using a clutch or the like.

[0136] In addition, it is possible for steer-by-wire steering system 200 to individually include a first control device that outputs a control signal from steering motor 410 and a second control device that outputs a control signal from counterforce motor 330.

[0137] In such a steering system 200, either the first control device or the second control device may include the control device that executes the vehicle behavior recognition process and may function as the vehicle behavior recognition device.

[0138] In addition, an electronic control device that does not have a function of controlling steering system 200 (in other words, counterforce motor 330 and steering motor 410) may include the control unit that executes the vehicle behavior detection process and may function as the vehicle behavior detection device. LIST OF REFERENCE SYMBOLS 100 vehicles 101, 102 Front road wheels 200 steering system 300 Steering control input device 340 Operating angle sensor 400 steering device 410 steering motor 421 Rack (movable element) 430 Rack stroke sensor 500 Steering control device (vehicle behavior detection device) 510 microcomputer (control unit) QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2011-093489 A

[0003]

Claims

[1] A vehicle behavior estimation method performed by a control unit mounted in a vehicle, the vehicle including a motor that applies steering torque to road wheels of the vehicle via a movable member, the vehicle behavior estimation method performed by the control unit comprising: Calculating a normative driving state of the vehicle from steering control information of a driver of the vehicle; Comparing the normative driving condition with a driving condition that actually occurs in the vehicle and outputting a first deviation; Calculating a normative axial force occurring in the movable element from a first physical quantity related to a traveling speed of the vehicle and a second physical quantity related to a steering angle of the road wheels; Calculating an estimated axial force generated in the movable member from a third physical quantity related to a current value of the motor; Comparing the normative axial force with the estimated axial force and outputting a second deviation; and Estimate the behavior of the vehicle by comparing the first deviation with the second deviation. [2] The vehicle behavior estimating method according to claim 1, wherein the control unit calculates an estimated axial force generated in the movable member from the third physical quantity and a fourth physical quantity related to a rotational speed of the motor. [3] The vehicle behavior estimation method according to claim 1, wherein the control unit calculates a normative yaw rate as the normative driving state from the steering operation information and the first physical quantity, and compares the normative yaw rate with a yaw rate actually occurring in the vehicle to output the first deviation. [4] The vehicle behavior estimation method according to claim 3, wherein the control unit provides a predetermined threshold value for the second deviation. [5] The vehicle behavior estimation method according to claim 4, wherein the control unit determines whether or not the vehicle is understeering or oversteering based on the first deviation, and when the second deviation is outside the predetermined threshold, determines that the first deviation is caused by a disturbance. [6] The vehicle behavior estimation method according to claim 4, wherein when the second deviation is not outside the predetermined threshold, the control unit determines whether or not the vehicle is understeering or oversteering based on the first deviation. [7] A vehicle behavior recognition device comprising the control unit that executes the vehicle behavior estimation method according to claim 1, wherein the control unit activates a warning device provided in the vehicle according to the estimated behavior of the vehicle. [8] A steering system comprising the vehicle behavior detecting device according to claim 7, the movable member, and the motor.

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