Steer-by-wire steering device, control device, and axial force estimation method

Abstract

According to a steer-by-wire steering device, a control device, and an axial force estimation method according to the present invention, a second current value for obtaining an estimated axial force generated in a movable member is calculated on the basis of a target movement speed of the movable member and an actual movement speed of the movable member. At least in a region in which the deviation between the target movement speed and the actual movement speed is smaller than a prescribed value, the second current value is calculated as a current value which is different from a first current value output to the motor in order to move the movable member on the basis of the target direction steering, and which has a smaller variation over a certain period of time than the first current value. As a result, it is possible to suppress a reduction in accuracy of axial force estimation due to a small displacement of a movable member such as a rack shaft.

Description

Technical Field

[0001] This invention relates to a steering device, a control device, and a method for estimating axial force in a steer-by-wire system. Background Technology

[0002] The electric power steering device of Patent Document 1 includes: an electric motor that applies an auxiliary force for steering the steering wheel of a vehicle; a rack shaft that rotates the wheel of the vehicle; and a control device that controls the driving force of the electric motor based on the deviation between the rate of change of the regulated rack shaft force that is a specification of the axial force generated on the rack shaft and the rate of change of the actual axial force generated on the rack shaft, i.e., the actual rack shaft force.

[0003] Prior technology documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-154632 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, in the position control of movable parts such as racks and pinions, even a small deviation between the target position and the actual position caused by a tiny displacement of the movable part will generate motor current for position control.

[0008] However, the minute displacement of the movable part is not reflected in the axial force of the movable part. Therefore, if the axial force of the movable part is estimated based on the motor current used for position control, there is a problem of reduced estimation accuracy of the axial force.

[0009] This invention was made in view of the existing situation, and its purpose is to provide a steerable device, control device, and axial force estimation method for steer-by-wire that can suppress the reduction in the accuracy of axial force estimation caused by small displacements of movable parts.

[0010] Methods for solving problems

[0011] In one embodiment of the steer-by-wire steering device, control device, and axial force estimation method involved in this invention, when calculating a second current value for determining the estimated axial force generated by the movable part based on the target moving speed and the actual moving speed of the movable part, at least in the region where the deviation between the target moving speed and the actual moving speed is less than a predetermined value, the second current value is calculated as a current value that is different from the first current value output to the motor to enable the movable part to move based on the target direction of steering, and has a smaller variation over a certain period of time compared to the first current value.

[0012] Invention Effects

[0013] According to the present invention, it is possible to suppress the decrease in the accuracy of axial force estimation caused by minute displacements of movable parts. Attached Figure Description

[0014] Figure 1 This is a schematic diagram representing a vehicle equipped with a steer-by-wire system.

[0015] Figure 2 It is a timing diagram that shows the variation of motor current due to the minute displacement of the rack shaft.

[0016] Figure 3 This is a module diagram of the first implementation of the calculation function representing the motor current.

[0017] Figure 4 It is a timing diagram showing the change of the second current value relative to the rack shaft in the first embodiment.

[0018] Figure 5 This is a module diagram representing the calculation function for estimating axial force.

[0019] Figure 6 It is a time series diagram showing the correlation between the axial force estimated based on the first current value, the axial force estimated based on the second current value, and the measured value of the axial force.

[0020] Figure 7 This is a module diagram of the second embodiment of the calculation function for motor current.

[0021] Figure 8 It is a timing diagram showing the change of the second current value relative to the rack shaft in the second embodiment. Detailed Implementation

[0022] Hereinafter, based on the accompanying drawings, embodiments of the steerable device, control device, and axial force estimation method of the present invention will be described.

[0023] Figure 1 This is a schematic diagram showing one configuration of a vehicle 100 equipped with a steer-by-wire system 200.

[0024] Vehicle 100 is a four-wheeled automobile with a pair of front wheels 101 and 102 on the left and right and a pair of rear wheels 103 and 104 on the left and right.

[0025] The steering apparatus 200 includes: a steering input device 300 that inputs steering (steering) operation of the driver of the vehicle 100 via a steering wheel 310; a wheel steering device 400 with a wheel steering motor 410 for imparting steering force to the steering wheels, i.e., the front wheels 101 and 102 of the vehicle 100; and a control device 500.

[0026] Here, the steering input device 300 and the wheel steering device 400 are mechanically separated. In other words, the steering wheel 310 and the steering wheels are mechanically separated.

[0027] The steering input device 300 includes a steering wheel 310, a steering shaft 320, a reaction motor 330, and an operating angle sensor 340.

[0028] The steering wheel 310 is a steering input component operated by the driver of the vehicle 100.

[0029] The reaction force motor 330 is an actuator that simulates the steering reaction torque applied to the steering wheel 310.

[0030] The operation angle sensor 340 detects the operation angle θ [deg] of the steering wheel 310.

[0031] The wheel steering device 400 includes a wheel steering mechanism 420.

[0032] The wheel steering mechanism 420 is a mechanism that converts the rotational motion of the wheel steering motor 410 into the linear motion of the rack shaft 421 through a gear and rack pair, thereby changing the steering angle (tire angle) of the front wheels 101 and 102 connected to the rack shaft 421.

[0033] That is, the wheel steering motor 410 applies steering force to the front wheels 101 and 102 via the rack shaft 421, which is a movable component.

[0034] In addition, the wheel steering device 400 includes a rack travel sensor 430 that detects the amount of travel of the rack shaft 421 related to the steering angle of the front wheels 101 and 102, i.e., rack travel RS [mm] (in other words, actual rack position), a motor rotation angle sensor 440 that detects the rotation angle θ m [deg] of the wheel steering motor 410, and a motor current sensor 450 that detects the current value Cm [Arms] of the wheel steering motor 410.

[0035] The control device 500 is an electronic control device equipped with an MCU (Micro Controller Unit) 510, which controls the action of the steering device 200 by controlling the reaction force motor 330 and the wheel steering motor 410, which are actuators of the steering device 200.

[0036] In addition, MCU510 can also be called a microcomputer, processor, processing device, computing device, etc.

[0037] The MCU510 processes various signals obtained from the outside to determine the control signals for the reaction force motor 330 and the wheel steering motor 410, and then outputs the determined control signals.

[0038] Here, the control device 500 may include a pre-drive, an inverter, etc., for controlling the energization of the reaction force motor 330 and the wheel steering motor 410.

[0039] In addition, it can be configured as a system that has a drive circuit including a pre-driver, an inverter, etc., independently of the control device 500.

[0040] In addition, the vehicle 100 is equipped with wheel speed sensors 621-624 that detect the rotational speed of each wheel 101-104, i.e., wheel speed WS1-WS4, front and rear acceleration sensors 630 that detect the front and rear acceleration G of the vehicle 100, and yaw rate sensor 640 that detects the yaw rate γ [deg / s] generated by the vehicle 100.

[0041] Furthermore, the MCU510 of the control device 500 acquires the output signals of the operating angle sensor 340, rack stroke sensor 430, motor rotation angle sensor 440, motor current sensor 450, wheel speed sensors 621-624, front and rear acceleration sensors 630, and yaw rate sensor 640.

[0042] Here, we outline the control content of the MCU510 of the control device 500 on the steering device 200, and more specifically, the control content of the reaction force motor 330 and the wheel steering motor 410.

[0043] Based on information such as the steering wheel 310's operating angle θ, the MCU510 calculates the target rack travel RStg (in other words, the target rack position or the target steering angle of the front wheels 101 and 102) as the target value of the rack shaft 421's travel amount.

[0044] Then, MCU510 calculates the target current of wheel steering motor 410 and outputs the control signal corresponding to the calculated target current to the drive circuit of wheel steering motor 410 so that the actual rack stroke RS (in other words, actual rack position, actual steering angle) detected by rack stroke sensor 430 is close to the target rack stroke RStg (in other words, target rack position, target steering angle).

[0045] Here, the MCU510 determines the target current of the wheel steering motor 410 through a combination of position control and speed control.

[0046] In detail, the MCU510 calculates the target rack travel speed ΔRStg based on the time derivative of the target rack travel RStg, i.e. the rate of change of the target rack travel RStg, and the rate of deviation between the target rack travel RStg and the actual rack travel RS.

[0047] Then, the MCU510 calculates the target current of the wheel steering motor 410 by proportional-integral (PI) control based on the control deviation (in other words, the comparison value) obtained by comparing the target rack travel speed ΔRStg and the actual rack travel speed ΔRS.

[0048] That is, the MCU510 adjusts the current of the wheel steering motor 410 by performing feedback control to correct the action so that the target moving speed of the rack shaft 421, which is a movable part, is consistent with the actual moving speed of the rack shaft 421.

[0049] Furthermore, although in this embodiment, the MCU510 uses the rack travel sensor 430 to detect the actual rack travel RS, the MCU510 can also calculate the actual rack travel RS based on the motor rotation angle θm detected by the motor rotation angle sensor 440.

[0050] In addition, the MCU510 can use a rotation angle sensor that detects the rotation angle of the pinion shaft to determine the actual rack travel RS.

[0051] Then, the MCU510 calculates the actual rack travel speed ΔRS by performing time differentiation on the actual rack travel RS.

[0052] In addition, the MCU510 can use the rotation angle signal of the reaction force motor 330 as information on the operation amount of the steering wheel 310.

[0053] Furthermore, if the steering input device 300 has a mechanism that converts the rotational motion of the steering shaft 320 into linear motion, the MCU 510 can obtain the signal from the sensor that detects the stroke of the movable part that performs linear motion according to the rotation of the steering shaft 320 as information on the operation amount of the steering wheel 310.

[0054] In addition, instead of setting the target rack travel RStg based on the information of the steering wheel 310's operation, the MCU510 can set the target rack travel RStg based on the target driving trajectory based on the external recognition results of the external recognition sensors mounted on the vehicle 100, as a function of autonomous driving and driving assistance.

[0055] In other words, the MCU 510 determines the direction of the target based on the amount of steering wheel 310 operation and the target driving trajectory.

[0056] In addition, in the control of the reaction torque by the reaction motor 330, the MCU510 calculates the reaction torque command value TRtg, which is the target value of the reaction torque TR, based on information such as the vehicle speed VS [km / h] obtained from the wheel speeds WS1-WS4 and the steering wheel 310 operating angle θ.

[0057] In addition, the MCU510 can obtain the wheel speed signals WS1-WS4 from the wheel speed sensors 621-624 to calculate the vehicle speed VS. Furthermore, other vehicle control devices can obtain the vehicle speed VS information calculated based on the wheel speed signals WS1-WS4 via the vehicle network.

[0058] Then, the MCU 510 outputs a control signal based on the reaction torque command value TRtg to the drive circuit of the reaction motor 330.

[0059] In this way, the MCU510 controls the operation of the steering device 200 by controlling the steering torque applied to the front wheels 101 and 102 and the reaction torque applied to the steering wheel 310.

[0060] Furthermore, the MCU510 has the function of estimating the axial force as an axial force generated in the rack shaft 421 by executing an axial force estimation method. The axial force of the rack shaft 421 obtained by the estimation process (hereinafter referred to as the estimated axial force) is used, for example, to estimate the friction coefficient μ of the road surface on which the vehicle 100 travels.

[0061] In detail, the MCU510 estimates the coefficient of friction μ of the road surface on which the vehicle 100 travels based on the estimated axial force of the rack shaft 421 and the axial force actually generated on the rack shaft 421.

[0062] Then, the MCU510 transmits the change in the road friction coefficient μ to the driver, for example, by correcting the reaction torque command value TRtg based on the estimated road friction coefficient μ.

[0063] In addition, the MCU510 can also add the estimated axial force to the reaction torque.

[0064] In addition, the MCU510 can also determine whether there are bumps or unevenness on the road surface based on the deviation between the standard axial force calculated from the actual rack travel RS and the vehicle speed and the estimated axial force, i.e., the axial force deviation.

[0065] Furthermore, when the MCU510 detects understeer or oversteer of the vehicle 100 based on the deviation between the standard yaw rate calculated from the wheel steering angle, vehicle speed, etc. and the actual yaw rate generated by the vehicle 100, if unevenness in the road surface is detected, the detection results of understeer or oversteer are invalidated.

[0066] Therefore, the detection accuracy of understeering and oversteering is reduced due to external interference such as uneven road surfaces.

[0067] Here, the MCU510 estimates the axial force based on the current of the wheel steering motor 410.

[0068] However, when the MCU510 directly uses the current supplied to the wheel steering motor 410 for the position control of the rack shaft 421 to calculate the estimated axial force, the accuracy of the axial force estimation may sometimes be reduced.

[0069] In other words, although the motor current used for position control of rack shaft 421 will change in response to the control deviation caused by the small displacement of rack shaft 421, the accuracy of axial force estimation will be reduced because such small displacement of rack shaft 421 is not reflected in the axial force of rack shaft 421.

[0070] Figure 2 It is a timing diagram showing how the motor current used for position control changes periodically in response to the periodic displacement when a small displacement of the rack shaft 421 is generated periodically.

[0071] Here, when MCU510 is used Figure 2 When the estimated axial force is calculated from the motor current (in other words, the actual motor current) used for position control, the estimated axial force will also change periodically. However, as mentioned above, since there is no actual change in axial force, the accuracy of the axial force estimation will be reduced.

[0072] Therefore, the MCU510 has the following functional unit (in other words, operational logic): it separately calculates the first current value of the motor current used for position control of the rack shaft 421 and the second current value of the motor current used for axial force estimation, and estimates the axial force based on the second current value, so that even when the rack shaft 421 is slightly displaced, the reduction in the estimation accuracy of the axial force can be suppressed.

[0073] Although explained in detail later, the second current value used for axial force estimation is calculated as a current value that varies less than the first current value over a certain period of time, at least in the region where the deviation between the target rack travel speed ΔRStg and the actual rack travel speed ΔRS is less than a specified value, unlike the first current value used for position control of rack shaft 421.

[0074] Here, if the MCU510 uses the second current value as the motor current for position control of the rack shaft 421, it will result in a decrease in the performance of position control.

[0075] In contrast, because the MCU510 calculates the motor current used for axial force estimation separately from the motor current used for position control of the rack shaft 421, it does not cause a reduction in position control performance and can calculate the estimated axial force with high accuracy.

[0076] Figure 3 This is a block diagram illustrating a first embodiment of the function of the MCU510 in calculating the current of the wheel steering motor 410.

[0077] The MCU510 has a first PI control unit 511 that functions as a motor current, i.e., a first current value, for calculating the position control of the rack shaft 421, and a second PI control unit 512 that functions as a motor current, i.e., a second current value, for calculating the axial force estimation.

[0078] The first PI control unit 511 and the second PI control unit 512 perform calculation processing to determine the current of the wheel steering motor 410 by PI control based on the deviation between the target rack travel speed ΔRStg and the actual rack travel speed ΔRS.

[0079] The first PI control unit 511 uses a proportional constant Kp1 and an integral constant Ki1 to implement PI control, while the second PI control unit 512 uses a proportional constant Kp2 and an integral constant Ki2 to implement PI control.

[0080] Here, by setting the integral constant Ki2 in the second PI control unit 512 to a value smaller than the integral constant Ki1 in the first PI control unit 511, the second PI control unit 512 is configured to calculate a second current value that reduces the responsiveness compared to the first current value for the common control deviation between the first PI control unit 511 and the second PI control unit 512.

[0081] In other words, the gain of the motor current of the second PI control unit 512 relative to the control deviation is smaller than that of the first PI control unit 511, and the second current value is calculated as a current value with a smaller change over a certain period of time compared with the first current value.

[0082] Furthermore, by setting at least one of the proportional constant Kp2 and the integral constant Ki2 to a value smaller than that of the proportional constant Kp1 and the integral constant Ki1, the gain of the motor current in the second PI control unit 512 relative to the control deviation can be made smaller than that in the first PI control unit 511.

[0083] That is, in order to make the rack shaft 421 movable based on the target direction of steering, the MCU510 calculates a first current value to be output to the wheel steering motor 410, and uses PI control based on control deviation to calculate a second current value that reduces the responsiveness compared to the first current value.

[0084] Figure 4 This is a timing diagram illustrating the change in the second current value when a small displacement of the rack shaft 421 occurs periodically.

[0085] and Figure 2 Compared to the motor current (first current value) used for position control shown, the gain of the second current value used for axial force estimation relative to the control deviation is suppressed to a lower value, so the variation of the small displacement relative to the rack shaft 421 becomes smaller.

[0086] Therefore, by calculating the estimated axial force based on the second current value, the MCU510 can suppress the estimation error of the estimated axial force to a smaller extent compared to the case where the estimated axial force is calculated based on the first current value.

[0087] The second PI control unit 512 outputs the calculated second current value signal to the rack axial force estimation unit 513.

[0088] Figure 5 This is a module diagram representing the calculation function of the estimated axial force [kN] based on the rack axial force estimation unit 513.

[0089] The rack axial force estimation unit 513 includes a friction compensation unit 513A, a friction compensation subtraction unit 513B, an axial force conversion unit 513C, a motor inertia compensation unit 513D, and an estimated axial force correction unit 513E.

[0090] Furthermore, based on the estimated axial force signal output by the axial force correction unit 513E, estimation processing of the road surface friction coefficient μ is performed.

[0091] The friction compensation unit 513A acquires a signal of a physical quantity related to the motor speed, namely the speed [rpm] of the wheel steering motor 410, and calculates the motor current value [Arms] of the mechanical friction amount based on the motor speed.

[0092] The friction compensation subtraction unit 513B obtains the signal of the second current value calculated by the second PI control unit 512, namely the motor current used for axial force estimation, and the signal of the current value of mechanical friction calculated by the friction compensation unit 513A.

[0093] Then, the friction compensation subtraction unit 513B subtracts the current value of mechanical friction from the motor current (second current value) used for axial force estimation, and outputs the subtraction result as the motor current value after the mechanical friction is corrected.

[0094] The axial force conversion unit 513C obtains the motor current value signal output by the friction compensation subtraction unit 513B, and calculates the basic estimated axial force estimated to be generated in the rack shaft 421 based on the obtained motor current value.

[0095] Furthermore, the conversion characteristic of the axial force conversion circuit 513C, which calculates the basic estimated axial force based on the motor current value, is set based on the rated torque, rated current, reduction ratio of the wheel steering motor 410, and the specific stroke (rack gain) in the wheel steering device 400.

[0096] The motor inertia compensation unit 513D acquires the rotational speed signal of the wheel steering motor 410 and calculates the axial force of the inertia of the wheel steering motor 410 based on the motor rotational speed.

[0097] The axial force estimation correction unit 513E obtains the signal of the basic estimated axial force obtained by the axial force conversion unit 513C, and the signal of the axial force of the inertia obtained by the motor inertia compensation unit 513D.

[0098] Then, the axial force correction unit 513E subtracts the axial force of inertia from the basic estimated axial force and outputs the subtraction result as the signal of the final estimated axial force.

[0099] Figure 6 It is a time series diagram showing the correlation between the axial force estimated based on the first current value, the axial force estimated based on the second current value, and the measured value of the axial force, indicating the change in axial force under conditions where a small change in rack position is generated that is not reflected in the axial force.

[0100] Here, although the actual axial force of the rack shaft 421 gradually increases over time, the axial force estimated based on the first current value picks up the tiny changes in the rack position that are not reflected in the axial force and thus produces an error relative to the measured value (actual axial force).

[0101] On the other hand, because the second current value suppresses the influence of the minute rack position changes that are not reflected in the axial force, the axial force estimated based on the second current value changes roughly along the measured value, becoming an estimate with the error sufficiently suppressed.

[0102] Figure 7 This is a block diagram illustrating a second embodiment of the motor current calculation function of the MCU510.

[0103] exist Figure 7 In the second embodiment shown, a deadband is set for the control deviation in the calculation and processing of the second current value.

[0104] Furthermore, in the dead zone region where the control deviation is smaller than the specified value, the second current value is different from the first current value and is calculated as a current value with smaller variation over a certain period of time compared to the first current value.

[0105] In detail, in the second embodiment, the MCU 510 calculates a second current value in which the change in current value is zero based on the difference between the control deviation, which is used as a comparison value, and a preset predetermined value.

[0106] exist Figure 7 In the second embodiment shown, MCU510 and Figure 3 Similar to the first embodiment shown, it has a first PI control unit 511 that calculates a first current value for position control of the rack shaft 421 and a second PI control unit 512 that calculates a second current value for axial force estimation.

[0107] In this second embodiment, the second PI control unit 512 has a coefficient setting unit 512A and a multiplication unit 512B in order to set the region near the zero control deviation as the dead zone in the calculation process of the second current value.

[0108] The coefficient setting unit 512A obtains a signal of the control deviation between the target rack travel speed ΔRStg and the actual rack travel speed ΔRS, and sets the coefficient based on the obtained control deviation.

[0109] Here, when the absolute value of the control deviation is below a specified value, that is, when the control deviation is within a specified range including zero, the coefficient setting unit 512A sets the coefficient to zero, and when the absolute value of the control deviation exceeds the specified value, the coefficient changes to 1.0.

[0110] The multiplication unit 512B obtains a signal of the control deviation between the target rack travel speed ΔRStg and the actual rack travel speed ΔRS.

[0111] Then, the multiplication unit 512B multiplies the control deviation by the coefficient set by the coefficient setting unit 512A, and outputs the multiplication result as the control deviation for PI control.

[0112] That is, when the coefficient is zero, the control deviation supplied for PI control in the second PI control unit 512 is zero, and when the coefficient is 1.0, the same value as the control deviation used for PI control in the first PI control unit 511 is supplied for PI control in the second PI control unit 512.

[0113] Therefore, even if the rack position repeatedly makes small displacements within a region where the absolute value of the control deviation is below the specified value, the control deviation supplied by the PI control will remain zero by setting the coefficient to zero.

[0114] Therefore, the region where the absolute value of the control deviation is below the specified value becomes the dead zone for the allowable control deviation, and the variation of the second current value becomes zero.

[0115] In the first PI control unit 511 that directly supplies the control deviation to the PI control, even if the absolute value of the control deviation is in the region below the specified value, the first current value will vary according to the small displacement of the rack shaft 421 that is not reflected in the axial force.

[0116] In contrast, in the second PI control unit 512, where the dead zone of the control deviation is set by the coefficient setting unit 512A and the multiplication unit 512B, even if a small control deviation occurs due to the small displacement of the rack shaft 421 that is not reflected in the axial force, the change in the second current value is zero.

[0117] In other words, the correlation between the control deviation and the coefficient in the adjustment coefficient setting unit 512A is adjusted so that the control deviation caused by the small displacement of the rack shaft 421 that is not reflected in the axial force becomes a dead zone.

[0118] Therefore, the minute displacement of the rack shaft 421, which is not reflected in the axial force, will not affect the axial force estimation (in other words, the second current value), thus improving the accuracy of the axial force estimation.

[0119] Figure 8 It is a timing diagram showing the change of the second current value when the rack shaft 421 periodically produces a small displacement in the second embodiment.

[0120] In the second embodiment, the control deviation caused by the minute displacement of the rack shaft 421 that is not reflected in the axial force is reset to zero, and the second current value remains fixed because it is not reflected in the second current value.

[0121] Therefore, the estimated axial force using the second current value also remains a fixed value relative to the small displacement of the rack shaft 421, suppressing the decrease in the estimation accuracy of the axial force with the small displacement of the rack shaft 421.

[0122] The technical ideas described in the above embodiments can be appropriately combined and used as long as they do not contradict each other.

[0123] Furthermore, the present invention has been specifically described with reference to preferred embodiments, but it is self-evident that those skilled in the art can adopt various modifications based on the basic technical ideas and teachings of the present invention.

[0124] For example, a system can be configured such that a second control device, which is another control device on the vehicle, obtains a signal of a second current value calculated by the control device 500 of the steering device 200 for determining the estimated axial force generated in the rack shaft 421 (movable part), and the second control device determines the estimated axial force.

[0125] In addition, the system can be configured as follows: a third control device, which is another control device on the vehicle, obtains a signal of the estimated axial force calculated by the control device 500 of the steering device 200 based on the second current value, and the third control device performs estimation processing of the road friction coefficient based on the estimated axial force.

[0126] In addition, in the second embodiment, the second PI control unit 512 sets the dead zone by multiplying the control deviation used for PI control by a coefficient corresponding to the control deviation. However, it is not limited to using the structure of the coefficient setting unit 512A and the multiplication unit 512B as long as the change in current value is set to zero in the region where the control deviation is below the specified value.

[0127] For example, it can be configured to switch between directly outputting the control deviation or outputting zero as the control deviation based on whether the control deviation is below a specified value.

[0128] Alternatively, it can be configured such that when the control deviation falls below a specified value, the updating of the second current value stops and remains at the current value before the control deviation falls below the specified value.

[0129] Explanation of reference numerals in the attached figures

[0130] 100…vehicle, 101, 102…front wheel, 200…steering device, 300…direction input device, 340…operating angle sensor, 400…wheel steering device, 410…wheel steering motor, 421…rack shaft (movable part), 430…rack travel sensor, 500…control device, 510…MCU.

Claims

1. A steer-by-wire type steering device, installed in a vehicle, having: The steering input device receives the driver's steering input. Wheel steering system, equipped with: A movable part, connected to the steering wheel of the vehicle, for turning the steering wheel; as well as A motor is used to impart steering force to the movable component; as well as The control device calculates a first current value output to the motor to enable the movable part to move based on the target directional steering, and calculates a second current value for determining the estimated axial force generated in the movable part based on the target moving speed and the actual moving speed of the movable part. The control device calculates the second current value as a current value that is different from the first current value and whose variation over a certain period of time is smaller than the first current value, at least in the region where the deviation between the target moving speed and the actual moving speed is smaller than a predetermined value.

2. The steer-by-wire type steering device according to claim 1, wherein, The control device compares the target moving speed of the movable part with the actual moving speed of the movable part, and uses PI control based on the comparison value obtained by comparison to calculate the second current value, which has a lower responsiveness than the first current value.

3. The steer-by-wire type steering device according to claim 1, wherein, The control device compares the target moving speed of the movable part with the actual moving speed of the movable part, and calculates the second current value with zero change based on the difference between the comparison value obtained by comparison and the preset value.

4. The steer-by-wire type steering device according to claim 1, wherein, The control device calculates the estimated axial force generated in the movable part based on the second current value and a physical quantity related to the rotational speed of the motor.

5. A control device disposed in a vehicle having a steer-by-wire type steering system. The steer-by-wire steering device has the following features: The steering input device receives the driver's steering input. as well as Wheel steering system, equipped with: A movable part, connected to the steering wheel of the vehicle, for turning the steering wheel; as well as A motor is used to impart steering force to the movable part. In the control device, Calculate the first current value output to the motor to enable the movable part to move based on the target directional steering. A second current value is calculated based on the target moving speed and the actual moving speed of the movable part to determine the estimated axial force generated in the movable part. At least in the region where the deviation between the target moving speed and the actual moving speed is smaller than a predetermined value, the second current value is calculated as a current value that is different from the first current value and whose variation over a certain period of time is smaller than that of the first current value.

6. A method for estimating axial force in a movable component, said axial force estimation method being performed by a control device in a vehicle equipped with a steer-by-wire steering system. The steer-by-wire steering device has the following features: The steering input device receives the driver's steering input. as well as Steering mechanism, equipped with: The movable component is connected to the steering wheel of the vehicle and is used to steer the steering wheel. as well as A motor is used to impart steering force to the movable part. In the axial force estimation method, A second current value is calculated based on the target moving speed and the actual moving speed of the movable part to determine the estimated axial force generated in the movable part. At least in the region where the deviation between the target moving speed and the actual moving speed is smaller than a predetermined value, the second current value is calculated as a current value that is different from the first current value and whose variation over a certain period of time is smaller than that of the first current value.

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