JP2006224804A - Vehicular steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular steering system capable of realizing excellent steering feeling by suppressing fluctuation of the steering reaction force. <P>SOLUTION: A control device controls the operation of a reaction force actuator so that the steering reaction force Fh to be given to the steering is maintained to be constant at that time when the applying direction of the road surface reaction force Fr to be estimated (detected) is the direction for increasing the turning angle. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a steer-by-wire vehicle steering apparatus.

  In recent years, the steered wheel and the steering (steering wheel) are mechanically separated, and based on the detected steering angle (steering angle), the steering wheel (steering angle) of the steered wheel according to the steering operation is generated. In order to achieve this, a so-called steer-by-wire vehicle steering apparatus that controls the operation of the steering actuator has been proposed.

  By the way, in such a steer-by-wire type vehicle steering apparatus, since the steered wheels and the steering are separated, the road surface reaction force acting on the steered wheels is not transmitted to the steering. Therefore, there is a problem that the driver cannot sense road surface information (road information) via the steering reaction force acting on the steering. Therefore, conventionally, the steering torque applied to the steering wheel by the steering operation and the road surface reaction force acting on the steered wheels are detected, and the reaction force to apply the steering reaction force according to the steering torque and the road surface reaction force to the steering wheel. Some control the operation of an actuator (see, for example, Patent Document 1). By adopting such a configuration, the road surface reaction force acting on the steered wheels can be reflected in the steering as the steering reaction force, and road surface information can be acquired through the steering operation, and it is better. It becomes possible to realize a smooth steering feeling.

  However, for example, it may not always be preferable to reflect all the road surface reaction forces acting on the steered wheels as steering reaction forces, such as when a rough road is passed. That is, in the case of a conventional steering apparatus having a mechanical steering transmission mechanism, a large road surface reaction force and a sudden change when the steered wheels pass through the unevenness on the road surface are directly transmitted to the steering as a steering reaction force. Such an excessive steering reaction force and its steep fluctuation hinder the steering operation and need not be faithfully reproduced.

Therefore, conventionally, a road surface reaction force reflecting mode that reflects the road surface reaction force as a steering reaction force and a release mode that does not reflect the road surface reaction force are provided, and these two modes can be switched according to the vehicle state. (See, for example, Patent Document 2). By adopting such a configuration, it becomes possible to prevent the deterioration of the steering feeling due to the excessive road surface reaction force at the time of passing through the unevenness being reflected in the steering reaction force.
JP 2004-34923 A JP 2003-182618 A

  However, as in the conventional example described above, when the configuration in which the reflection of the road surface reaction force on the steering is simply cancelled, the steering reaction force rapidly decreases by the amount corresponding to the road surface reaction force with the cancellation. As a result, for example, a so-called rudder feeling may occur due to a decrease in the steering reaction force, which may cause a deterioration in steering feeling. In this respect, there is still room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle steering apparatus that can realize a favorable steering feeling by suppressing fluctuations in steering reaction force. There is.

  In order to solve the above-mentioned problems, the invention according to claim 1 is directed to a steering mechanically separated from the steered wheels, and to be controlled to generate a steered angle of the steered wheels according to the steering operation. A rudder actuator, a reaction force actuator for applying a steering reaction force to the steering, a road surface reaction force detection means for detecting a road surface reaction force acting on the steered wheels, and the road surface reaction force according to the detected road surface reaction force A vehicle steering apparatus comprising: a control unit that controls the operation of the reaction force actuator to apply a steering reaction force to the steering, wherein the control unit applies the detected road surface reaction force in the direction The gist is to control the operation of the reaction force actuator so that the applied steering reaction force is constant at the detected value when the turning angle is increased.

  According to the above configuration, the steering reaction force applied to the steering is maintained at the value at the time when the steered wheels enter the rudder or at the time of the puncture even when the “wadachi” passes or puncture occurs (the steering reaction force). Holding control). As a result, it is possible to prevent a feeling of rudder slipping and an excessive steering angle, and as a result, a situation where the vehicle deviates from the lane due to the so-called “steering in the“ cutting direction ”by rutting or puncture”. Can be effectively suppressed.

  According to a second aspect of the present invention, when the control means applies the detected road surface reaction force in a direction in which the turning angle is decreased and the rate of change is greater than a predetermined value, The gist of the invention is to control the operation of the reaction force actuator so that the steering reaction force to be applied is constant at the detected value.

  According to the above configuration, even if a phenomenon such as “the steering is brought back in the“ turnback direction ”” occurs due to a sudden increase in the steering reaction force against the steering operation, the steering angle of the steering is reduced. It is possible to prevent sudden changes and effectively prevent a situation in which the vehicle leaves the lane.

  According to a third aspect of the present invention, the control means stores a value of the road surface reaction force at a time when the steering reaction force is constant, and a current value of the detected road surface reaction force is the stored value. The gist is to control the operation of the reaction force actuator so that the steering reaction force remains constant until equal.

  According to the above configuration, since the value of the steering reaction force at the end of the steering reaction force holding control is equal to the value reflecting the current road surface reaction force, the fluctuation of the steering reaction force can be suppressed even during the switching. A good steering feeling can be secured.

  ADVANTAGE OF THE INVENTION According to this invention, the steering apparatus for vehicles which can suppress the fluctuation | variation of steering reaction force and can implement | achieve favorable steering feeling can be provided.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment in which the present invention is embodied in a steer-by-wire vehicle steering device (steering device) will be described with reference to the drawings.
As shown in FIG. 1, in the steering device 1 of this embodiment, a steering mechanism 3 including a steering (handle) 2 and a steering mechanism 5 for changing the steering angle of the steered wheels 4 are mechanically disconnected. That is, this is a so-called steer-by-wire vehicle steering device in which the steering wheel 2 and the steered wheels 4 are mechanically separated.

  The steering mechanism 3 includes a steering shaft 6 to which the steering wheel 2 is fixed, and a steering angle sensor 7 as a steering angle detection means for detecting a steering angle of the steering wheel 2 in accordance with a steering operation, that is, a steering angle θs. . The steering mechanism 5 includes a steering actuator 8 for generating a steering angle of the steered wheels 4 corresponding to the steering operation based on the steering angle θs detected by the steering angle sensor 7. In this embodiment, the steered mechanism 5 has a steered shaft 12 that connects the left and right steered wheels 4 via a tie rod 9 and a knuckle arm 10, and the steered actuator 8 is a motor 13 as a drive source. And a conversion mechanism 14 that converts the rotation of the motor 13 into the reciprocating motion of the steered shaft 12. The steered actuator 8 of this embodiment includes a brushless motor that is coaxially disposed with the steered shaft 12 and includes a ball screw mechanism as the conversion mechanism 14. Then, the reciprocating motion of the steered shaft 12 driven by the steered actuator 8 is transmitted to the steered wheels 4, so that the steered angle of the steered wheels 4, that is, the steered angle θt is changed. Yes.

  In the present embodiment, the steering mechanism 3 includes a torque sensor 16 as a steering torque detection means for detecting the steering torque τ applied to the steering wheel 2 by a steering operation, and the detected steering torque τ (and will be described later). And a reaction force actuator 17 for applying a steering reaction force corresponding to the road surface reaction force Fr) to the steering wheel 2. The reaction force actuator 17 includes a motor 18 as a drive source and a speed reduction mechanism 19 that decelerates the rotation of the motor 18 and transmits it to the steering shaft 6. In the present embodiment, a brushless motor is employed as the motor 18 of the reaction force actuator 17 in the same manner as the motor 13 of the steering actuator 8. The reaction force actuator 17 transmits a motor torque generated by the motor 18 to the steering shaft 6 via the speed reduction mechanism 19 to apply a steering reaction force to the steering 2.

  In the present embodiment, the operation of the steering actuator 8 and the reaction force actuator 17 is controlled by the control device 20. More specifically, the motor 13 of the steering actuator 8 and the motor 18 of the reaction force actuator 17 are connected to the control device 20, and each of the motors 13 and 18 has three phases (U, V) supplied from the control device 20. , W) based on the driving power. And the control apparatus 20 controls the action | operation of the steering actuator 8 and the reaction force actuator 17 by controlling rotation of each motor 13 and 18 through the supply of the drive electric power. Specifically, the control device 20 detects the steering angle θs, the steering torque τ, and the vehicle speed V based on the output signals from the steering angle sensor 7, the torque sensor 16, and the vehicle speed sensor 21. Further, the turning shaft 12 is provided with a displacement amount sensor 22, and the control device 20 determines the turning angle θt of the steered wheels 4 based on the output signal of the displacement amount sensor 22. Twelve axial displacement amounts X are detected. Then, the control device 20 controls the operation of the steered actuator 8 to change the steered angle θt of the steered wheels 4 based on the detected steering angle θs, vehicle speed V, and displacement X, and the steering torque τ Based on the vehicle speed V (and the road surface reaction force Fr), the operation of the reaction force actuator 17 is controlled to apply the steering reaction force.

  Next, control modes of the steering actuator 8 and the reaction force actuator 17 by the control device 20 will be described. FIG. 2 is a control block diagram of the steering device 1 of the present embodiment. As shown in the figure, the control device 20 includes a first ECU 23 for controlling the steering actuator 8 and a second ECU 24 for controlling the reaction force actuator 17. The first ECU 23 and the second ECU 24 supply microcomputers 25 and 26 that output motor control signals for controlling the motors 13 and 18, respectively, and supply driving power to the motors 13 and 18 based on the motor control signals. Drive circuits 27 and 28. Each control block in the microcomputers 25 and 26 shown below is realized by a computer program executed by the microcomputers 25 and 26.

  First, the configuration of the microcomputer 25 on the first ECU 23 side that controls the steering actuator 8 will be described. The microcomputer 25 is based on the displacement amount command calculation unit 31 that generates the displacement amount command X * of the steered shaft 12 corresponding to the control target angle of the steered wheels 4, the displacement amount command X *, and the detected displacement amount X. A position control calculation unit 32 that calculates the position control amount ε, and a motor control signal generation unit 33 that generates a motor control signal to be output to the drive circuit 27 based on the position control amount ε.

  The steering angle θs and the vehicle speed V are input to the displacement amount command calculating unit 31, and the displacement amount command calculating unit 31 generates a displacement amount command X * based on the steering angle θs and the vehicle speed V, and the displacement amount command X * is output to the position control calculation unit 32. The displacement control unit 32 receives the displacement X detected by the displacement sensor 22 together with the displacement command X *. Then, the position control calculation unit 32 calculates the position control amount ε by feedback control based on the displacement amount command X * and the displacement amount X, and outputs the position control amount ε to the motor control signal generation unit 33. In addition to the position control amount ε calculated by the position control calculation unit 32, the motor control signal generation unit 33 receives the actual current value detected by the current sensor 34 and the rotation angle of the motor 13 detected by the rotation angle sensor 35. Is done. The motor control signal generation unit 33 generates a motor control signal based on the position control amount ε, the actual current value, and the rotation angle, and outputs the motor control signal to the drive circuit 27. Then, when a drive current corresponding to the motor control signal is supplied to the motor 13, the rotation of the motor 13, that is, the operation of the turning actuator 8, causes the turning angle θt of the steered wheels 4 to follow the control target angle. Is to be controlled.

  On the other hand, the microcomputer 26 on the second ECU 24 side that controls the reaction force actuator 17 controls the steering reaction force command Iq * as a control target amount of the steering reaction force Fh applied to the steering 2, that is, a current command value of the drive current supplied to the motor 18. And a motor control signal generation unit 42 that generates a motor control signal to be output to the drive circuit 28 based on the steering reaction force command Iq *.

  In the present embodiment, the microcomputer 26 includes a road surface reaction force estimation calculation unit 43 that estimates the road surface reaction force Fr acting on the steered wheels 4, and the steering reaction force command calculation unit 41 estimates the road surface reaction force. A steering reaction force command Iq * is calculated based on the road surface reaction force Fr estimated by the calculation unit 43. That is, in the present embodiment, the road surface reaction force estimation calculation unit 43 constitutes a road surface reaction force detection means. Then, drive power based on the steering reaction force command Iq * is supplied to the motor 18, that is, the operation of the reaction force actuator 17 is controlled, and the road reaction force Fr acting on the steered wheels 4 is controlled (road surface reaction force Fr). The steering reaction force Fh is reflected on the steering 2.

  More specifically, in the present embodiment, the road surface reaction force estimation calculation unit 43 has the displacement X and the actual current value detected by the current sensor 34, that is, the actual current supplied to the motor 13 on the steering actuator 8 side. A value is entered. Then, the road surface reaction force estimation calculation unit 43 calculates an axial force acting on the steered shaft 12 based on the displacement amount X and the actual current value, and the road surface reaction force Fr acting on the steered wheel 4 with the axial force. presume. A steering torque τ and a vehicle speed V are input to the steering reaction force command calculation unit 41 together with the road surface reaction force Fr estimated by the road surface reaction force estimation calculation unit 43. The steering reaction force command calculation unit 41 calculates a steering reaction force command Iq * based on the steering torque τ, the road surface reaction force Fr, and the vehicle speed V, and the steering reaction force command Iq * is calculated as a motor control signal generation unit. Output to 42. The motor control signal generator 42 is supplied with the steering reaction force command Iq * and the actual current value detected by the current sensor 44 and the rotation angle of the motor 18 detected by the rotation angle sensor 45. Then, the motor control signal generation unit 42 generates a motor control signal based on the steering reaction force command Iq *, the actual current value, and the rotation angle, and outputs the motor control signal to the drive circuit 28. Then, a driving current having a current value corresponding to the motor control signal is supplied to the motor 18, so that the steering torque τ, the road surface reaction force Fr, and the steering reaction force Fh corresponding to the vehicle speed V are applied to the steering 2. It has come to be.

(Steering reaction force retention control)
Next, steering reaction force holding control by the control device of the present embodiment will be described.
As described above, it is not always preferable to reflect all of the road surface reaction force acting on the steered wheels as the steering reaction force. For example, when traveling on rough roads, when the steered wheels 4 pass through irregularities on the road surface or when any wheel of the vehicle punctures, the road surface reaction force Fr is reflected in the steering reaction force as it is. An excessively and steeply changing steering reaction force is applied to the steering 2, and the steering feeling may be greatly impaired due to the fluctuation. In particular, when a road surface reaction force Fr in a direction that increases the steering angle (absolute value of the steering angle θt) is applied to the steered wheels 4, a steering reaction force in the same direction as the operation direction is applied to the steering 2. As a result, a phenomenon that causes the driver to feel uneasy, such as generation of a so-called rudder feeling or excessive generation of the steering angle θs in the increasing direction (cutting direction) of the steering angle θs, is likely to be induced.

  In consideration of this point, in the steering device 1 of the present embodiment, the control device 20 allows the reaction force actuator 17 of the reaction force actuator 17 to keep the steering reaction force applied to the steering wheel 2 at a value at that time under a predetermined condition. Control the operation. Specifically, when the application direction of the estimated (detected) road reaction force Fr is a direction that increases the turning angle θt, or even when the application direction is a direction that decreases the turning angle θt, the change is made. When the speed is higher than a predetermined value, the steering reaction force applied to the steering 2 is held constant at the value at that time (steering reaction force holding control). As a result, it is possible to suppress the occurrence of a feeling of rudder that causes the driver to feel uneasy or the occurrence of an excessive steering angle θs.

[Steering reaction force retention function]
First, the steering reaction force holding function of the microcomputer 26 in this embodiment will be described.
As shown in FIG. 2, the microcomputer 26 according to the present embodiment applies a holding determination unit 46 that performs on / off determination (holding determination) of the steering reaction force holding control, and a constant steering reaction force during the steering reaction force holding control. And a steering reaction force command holding unit 47 that outputs a holding steering reaction force command Iq_s *, which is a control target amount for the control. When the holding determination unit 46 determines that the steering reaction force holding control is “ON”, the steering reaction force command Iq * (current value) output from the steering reaction force command calculation unit 41 is used instead of the steering reaction force command Iq * (current value). A motor control signal based on the holding steering reaction force command Iq_s * (holding value) output from the command holding unit 47 is output to the drive circuit 28.

  More specifically, in the present embodiment, the holding determination unit 46 receives the road surface reaction force Fr output from the road surface reaction force estimation calculation unit 43, the steering angle θs, and the vehicle speed V. The determination unit 46 performs the holding determination based on the input road surface reaction force Fr, steering angle θs (steering speed ωs), and vehicle speed V (differential value αV). Then, the determination result is output to the steering reaction force command holding unit 47 as a holding signal Sh. In this embodiment, the holding determination unit 46 sets a holding flag when the steering reaction force holding control is “ON” (holding signal Sh = “ON”), and the steering reaction force holding control is “OFF”. When (holding signal Sh = “OFF”), the holding flag is reset.

  A steering reaction force command Iq * calculated by the steering reaction force command calculation unit 41 is input to the steering reaction force command holding unit 47 together with the holding signal Sh. When “ON”, the steering reaction force command Iq * at that time is stored as the holding steering reaction force command Iq_s *. Then, the steering reaction force command holding unit 47 outputs this holding steering reaction force command Iq_s * until the input holding signal Sh is “OFF”, that is, the holding flag is reset. In this embodiment, the steering reaction force command Iq * output from the steering reaction force command calculation unit 41 and the holding steering reaction force command Iq_s * output from the steering reaction force command holding unit 47 are output together with the holding signal Sh. 48 is input. When the holding signal Sh is “off”, the output switching unit 48 outputs the steering reaction force command Iq * output from the steering reaction force command calculation unit 41 to the motor control signal generation unit 42, and holds the holding signal Sh. Is “on”, the holding steering reaction force command Iq_s * output from the steering reaction force command holding unit 47 is output to the motor control signal generation unit 42.

  That is, as shown in the flowchart of FIG. 3, the microcomputer 26 first detects the displacement value X, the actual current value Is, the steering angle θs (steering speed ωs), and the vehicle speed V (differential values thereof) as sensor values (vehicle state quantities). (αV) is acquired (step 101), the road surface reaction force Fr is estimated (step 102), and the steering reaction force command Iq * for applying the steering reaction force corresponding to the road surface reaction force Fr to the steering is calculated. Is executed (step 103). Then, the microcomputer 26 makes an on / off determination (holding determination) for the steering reaction force holding control based on the estimated road surface reaction force Fr, the steering angle θs (steering speed ωs), and the vehicle speed V (its differential value αV). Execute (step 104).

  Next, the microcomputer 26 determines whether or not the steering reaction force retention control is determined to be “on” in the retention determination in step 104 (step 105), and if the determination is “on” (step 105). 105: YES), it is subsequently determined whether the steering reaction force holding control is being executed, that is, whether it is already being held (step 106). The determination as to whether or not the data is being held is made based on whether or not the holding flag is set.

  Next, when the microcomputer 26 determines in step 106 that the vehicle is not being held, that is, when the steering reaction force holding control is started (step 106: NO), the microcomputer 26 sets a holding flag (step 107). The steering reaction force command Iq * at that time is stored as a holding value, that is, a holding steering reaction force command Iq_s * (step 108). Then, a motor control signal based on the hold value (holding steering reaction force command Iq_s *) is output to the drive circuit 28 (step 109). On the other hand, if the microcomputer 26 determines in step 106 that it is already being held (step 106: YES), the microcomputer 26 does not execute the processing in steps 107 and 108, but in step 109, the holding value (holding steering). A motor control signal based on the reaction force command Iq_s *) is output.

  On the other hand, if it is determined in step 105 that the determination in step 104 is “OFF” (step 105: NO), the microcomputer 26 subsequently determines whether or not it is being held (step 110). If it is determined in step 110 that the vehicle is being held (step 110: YES), the holding flag is reset (step 111), and the steering reaction force command Iq * calculated in step 103, that is, the current A motor control signal based on the current value reflecting the road surface reaction force Fr is output to the drive circuit 28 (step 112). If it is determined in step 110 that the motor is not being held (step 110: NO), the motor based on the current value (steering reaction force command Iq *) is not executed in step 112 without executing step 111. A control signal is output to the drive circuit 28.

  By this series of processing, during the steering reaction force holding control, the steering reaction force corresponding to the holding value (holding steering reaction force command Iq_s *), that is, the road surface reaction force Fr when the steering reaction force holding control is started. A constant steering reaction force based on the above is applied to the steering wheel 2, and a steering reaction force corresponding to the current value (steering reaction force command Iq *) is applied after the completion of the steering reaction force holding control.

[Retention judgment]
Next, a holding determination processing procedure in the holding determination unit 46 will be described.
As shown in the flowchart of FIG. 4, the holding determination unit 46 first determines whether or not a continuation flag to be described later is set (step 201). If it is determined in step 201 that the continuation flag is not set (step 201: NO), the following start determination processing in steps 202 to 208 and step 210 is executed.

  Specifically, the holding determination unit 46 first performs an application exclusion determination of the steering reaction force holding control (steps 202 to 205). Specifically, whether or not the vehicle speed V is faster than a predetermined speed V0 (for example, V0 = 5 km / hour) (step 202), the differential value αV of the vehicle speed V is substantially zero (for example, αV ≦ 0.05). Whether or not the steering speed ωs is substantially zero (for example, ωs ≦ 0.001 rad / sec) (step 204). Further, it is determined whether or not the road surface reaction force Fr, specifically, the absolute value of the current value Fr_c exceeds a predetermined threshold value Vts (step 205). In the present embodiment, the steering speed ωs is obtained by differentiating the steering angle θs.

  Then, when all of the determination conditions in steps 202 to 205 are satisfied, the holding determination unit 46 subsequently applies the road surface reaction force Fr (current value Fr_c) to the steered angle of the steered wheels 4 (the steered angle θt). It is determined whether or not the direction is to increase (absolute value) (step 206). In other words, in the present embodiment, the holding determination unit 46 determines that the vehicle is not traveling at an extremely low speed (V> V0, Step 202: YES), not during acceleration / deceleration (αV≈0, Step 203: YES), and the steering angle. When not changing (ωs≈0, step 204: YES), but when the current value Fr_c (absolute value) of the road surface reaction force Fr exceeds a predetermined threshold Vts (| Fr_c |> Vts, step 205: YES), The main determination of the start determination process is executed.

  Specifically, in the present embodiment, the holding determination process (and acquisition of the sensor value) in the holding determination unit 46 is performed every predetermined cycle (for example, about 10 μsec), and the holding determination unit 46 The value of the road surface reaction force Fr detected in the previous processing cycle is stored as the previous value Fr_b. In step 206, the holding determination unit 46 determines whether the absolute value (| Fr_b + Fr_c |) of the sum of the previous value Fr_b and the current value Fr_c is greater than the absolute value (| Fr_b |) of the previous value Fr_b. By the determination, it is determined whether or not the application direction of the road surface reaction force Fr (current value Fr_c) is a direction in which the turning angle θt is increased. When the holding determination unit 46 determines that the application direction of the road surface reaction force Fr (current value Fr_c) is a direction in which the turning angle θt is increased (| Fr_b + Fr_c |> | Fr_b |, step 206: YES). Sets the continuation flag (step 207), and stores the value of the road surface reaction force Fr at that time, that is, the current value Fr_c as a stored value Fr_m described later (step 208). Then, in order to turn on the steering reaction force holding control, the holding signal Sh to be output is set to “ON” (step 209).

  If it is determined in step 206 that the road surface reaction force Fr (current value Fr_c) is applied in the direction in which the turning angle θt is decreased (| Fr_b + Fr_c | ≦ | Fr_b |, step 206: NO), it is retained. Subsequently, the determination unit 46 determines whether or not the change amount (| Fr_b−Fr_c |) of the current value Fr_c with respect to the previous value Fr_b is larger than a predetermined threshold δ (for example, 20N) (step 210). When the change amount (absolute value) of the current value Fr_c with respect to the previous value Fr_b is larger than the predetermined threshold δ (| Fr_b−Fr_c |> δ, Step 210: YES), the processing of Steps 207 to 209 is performed. Execute. That is, in this embodiment, even if the application direction of the road surface reaction force Fr (current value Fr_c) is a direction in which the turning angle θt is decreased, the current value Fr_c with respect to the previous value Fr_b per unit time (per cycle). When the change amount (absolute value) of the vehicle is larger than the predetermined threshold value δ, in other words, when the change speed of the road surface reaction force Fr is larger than the predetermined value, the steering reaction force holding control is turned on. The output holding signal Sh is set to “ON”. As a result, even when the road surface reaction force Fr applied to the steered wheels 4 changes steeply, the steering reaction force holding control is turned “on”, and a constant steering reaction force based on the road surface reaction force Fr at that time is maintained. It is given to the steering 2.

  In the present embodiment, the holding determination unit 46 accelerates or decelerates when any of the determination conditions of the above steps 202 to 205 is not satisfied, that is, when the vehicle is traveling at an extremely low speed (V ≦ V0, step 202: NO). Time (step 203: NO) or when the steering angle is changed (step 204: NO), or when the current value Fr_c (absolute value) of the road surface reaction force Fr is equal to or less than a predetermined threshold Vts (| Fr_c | ≦ Vts, step 205: NO), the processing of step 206 to step 210 is not executed. Further, when it is determined in step 210 that the change amount (absolute value) of the current value Fr_c with respect to the previous value Fr_b is equal to or less than a predetermined threshold δ (| Fr_b−Fr_c | ≦ δ, step 210: NO) Steps 207 to 209 are not executed. In these cases, the holding determination unit 46 sets the output holding signal Sh to “OFF” to turn the steering reaction force holding control “off” (step 211).

  On the other hand, if it is determined in step 201 that the continuation flag is set (step 201: YES), that is, if it is determined that the steering reaction force holding control has already been started, the holding determination unit 46 When it is determined whether the detected current value Fr_c of the road surface reaction force Fr is equal to the stored value Fr_m (step 212), and it is determined that the current value Fr_c is not equal to the stored value Fr_m (step 212: NO) Performs the process of step 209. If it is determined that the current value Fr_c is equal to the stored value Fr_m (Fr_c = Fr_m, step 212: YES), the continuation flag is reset (step 213), and the stored value Fr_m is initialized (step 214). In order to turn off the steering reaction force holding control, the holding signal Sh to be output is set to “OFF” (step 211). Then, after executing the processing in step 209 or step 211, the holding determination unit 46 stores the current value Fr_c as the previous value Fr_b used for the next holding determination process (Fr_b = Fr_c, step 215).

  That is, in the present embodiment, the continuation flag set in step 207 is not reset until it is determined in step 212 that the current value Fr_c is equal to the stored value Fr_m, and during that time, the holding signal Sh is “ON”. . Thus, a constant steering reaction based on the stored value Fr_m is maintained until the detected current value of the road surface reaction force Fr becomes equal to the stored value Fr_m that is a value at the time when the steering reaction force holding control is started. A force is applied to the steering 2.

(Action / Effect)
Next, operations and effects of the steering device 1 of the present embodiment configured as described above will be described. As shown in FIG. 5, for example, when turning left, that is, when the driver is performing a steering operation in the left direction (minus direction in the figure), the steered wheels 4 have a steering angle generated by the steering operation. A road surface reaction force Fr in the direction returning to the neutral position (steering angle θt = 0), that is, the right direction (the plus direction in the figure) opposite to the steering operation direction is applied. Accordingly, in this case, a steering reaction force Fh in the right direction reflecting the road surface reaction force Fr is applied to the steering 2.

  Here, a disturbance that causes the steered wheel 4 to increase its rudder angle by passing through the “wadder” on the road surface (stress acting when the steered wheel 4 tries to move along the shape of the rudder) ) Is applied, the road surface reaction force Fr changes to the same left direction as the steering operation direction. Therefore, if the change in the road surface reaction force Fr is directly applied to the steering wheel 2 as the steering reaction force Fh, a feeling of steering loss occurs due to a sudden decrease in the steering reaction force Fh against the steering operation. Alternatively, when the steering reaction force Fh is applied in the same direction as the steering operation direction, an excessive steering angle θs is generated, that is, a phenomenon such as “the steering is brought in the“ cutting direction ”” occurs. .

  In this regard, the steering device 1 according to the present embodiment determines the steering reaction force Fh to be applied to the steering 2 at that time when the application direction of the estimated (detected) road surface reaction force Fr is a direction that increases the turning angle θt. Keep constant at the value of. For this reason, the steering reaction force Fh is maintained at a value immediately after the steered wheels 4 have entered immediately, thereby preventing the feeling of steering omission and excessive steering angle θs. As a result, it is possible to effectively suppress a situation in which the vehicle deviates from the lane due to the so-called “steering immediately”. In addition, after the start of the steering reaction force holding control, the current value of the detected road surface reaction force Fr is based on the value at the start time until the current value of the road surface reaction force Fr becomes equal to the value at the time when the steering reaction force holding control is started. A constant steering reaction force Fh is applied to the steering 2. Therefore, even when switching from the steering reaction force holding control to the normal control, that is, the control to apply the steering reaction force Fh reflecting the current road surface reaction force Fr, a suitable steering feeling is suppressed by suppressing the fluctuation at the time of switching. Can be secured.

  Furthermore, when any wheel of the vehicle including both steered wheels 4 is punctured, the road surface reaction force Fr changes more rapidly. In this respect, the steering device 1 according to the present embodiment provides the steering to be applied to the steering 2 when the application speed of the road surface reaction force Fr is a direction in which the turning angle θt is decreased and the change speed is larger than a predetermined value. The reaction force Fh is kept constant at the value at that time. For this reason, as shown in the figure, even if a phenomenon such as “the steering is brought back in the“ turnback direction ”” occurs due to a sudden increase in the steering reaction force Fh against the steering operation. Thus, the sudden change of the steering angle θs of the steering wheel 2 can be prevented, and the situation where the vehicle deviates from the lane can be effectively prevented.

In addition, you may change this embodiment as follows.
In the present embodiment, the control device 20 as the control means includes a first ECU 23 for controlling the steering actuator 8 and a second ECU 24 for controlling the reaction force actuator 17. However, the present invention is not limited to this, and the control means for controlling the steered actuator 8 and the reaction force actuator 17 may have a configuration in which components corresponding to the first ECU 23 and the second ECU 24 are provided separately.

  In the present embodiment, the control device 20 controls the operation of the steered actuator 8 to change the steered angle θt of the steered wheels 4 based on the detected steering angle θs, vehicle speed V, and displacement amount X. It was. However, the present invention is not limited to this, and the steered actuator 8 only needs to be controlled based on at least the steering angle θs. The control device 20 controls the operation of the reaction force actuator 17 to apply the steering reaction force based on the steering torque τ and the vehicle speed V (and the road surface reaction force Fr). The parameters other than the road surface reaction force Fr are not limited to the steering torque τ and the vehicle speed V as long as a corresponding steering reaction force can be applied.

  In each of the above embodiments, the road surface reaction force estimation calculation unit 43 determines the turning shaft 12 based on the displacement amount X detected by the displacement amount sensor 22 and the actual current value of the motor 13 that is the drive source of the turning actuator 8. The axial force acting on the vehicle is calculated, and the axial force is estimated as the road surface reaction force Fr acting on the steered wheels 4. However, the present invention is not limited to this, and the road surface reaction force Fr may be estimated using the position control amount ε calculated by the position control calculation unit 32.

  Further, the control device 20 controls the operation of the reaction force actuator using the estimated road surface reaction force Fr, but the road surface reaction force Fr acts on the steered shaft 12 using a strain gauge or the like. A configuration may be adopted in which the road surface reaction force Fr is directly detected, such as detecting an axial force.

In addition, the displacement amount X is not necessarily detected by the displacement amount sensor 22 and may be estimated from the rotation angle of the motor 13 detected by the rotation angle sensor 35.
The mode and processing procedure of the holding determination in the holding determination unit 46 are not limited to those shown in the flowchart of FIG. For example, each application exclusion determination (step 202 to step 205) in the figure is not necessarily performed, and the determination content may be arbitrarily changed. Further, in the present embodiment, it is determined whether or not the application direction of the road surface reaction force Fr (current value Fr_c) in step 206 is a direction in which the steered angle of the steered wheels 4 (the absolute value of the steered angle θt) is increased. The absolute value (| Fr_b + Fr_c |) of the sum of the previous value Fr_b and the current value Fr_c is determined by determining whether or not the absolute value (| Fr_b |) of the previous value Fr_b is larger. However, the present invention is not limited to this, and the steering operation direction may be determined from the sign of the steering angle θs (θs> 0?), And the sign of the current value Fr_c (Fr_c> 0?) May be determined.

  In this embodiment, after the start of the steering reaction force holding control, until the current value of the detected road reaction force Fr becomes equal to the value at the time when the steering reaction force holding control is started, A constant steering reaction force Fh based on the value is applied to the steering 2 (see FIG. 5). However, the present invention is not limited to this, and, for example, a configuration in which a predetermined time is maintained from the start of the steering reaction force holding control may be employed.

The schematic block diagram of a steering device. The control block diagram of a steering device. The flowchart which shows the output processing procedure of a motor control signal. The flowchart which shows the process sequence of holding | maintenance determination. Action | operation explanatory drawing which shows the aspect of steering reaction force holding | maintenance control.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 2 ... Steering (handle), 3 ... Steering mechanism, 4 ... Steering wheel, 5 ... Steering mechanism, 6 ... Steering shaft, 7 ... Steering angle sensor, 8 ... Steering actuator, 12 ... Steering shaft , 16 ... torque sensor, 17 ... reaction force actuator, 20 ... control device, 21 ... vehicle speed sensor, 22 ... displacement sensor, 24 ... second ECU, 26 ... microcomputer, θs ... steering angle, θt ... turning angle, τ ... Steering torque, V: Vehicle speed, X: Displacement amount, Fr: Road reaction force, Fr_c: Current value, Fr_b: Previous value, Fr_m: Memory value, Fh: Steering reaction force, Sh: Holding signal, Iq *: Steering reaction force Command, Iq_s *: Holding steering reaction force command, Vts, δ: Threshold value.

Claims (3)

Steering that is mechanically separated from the steered wheels, a steered actuator that is controlled to generate a steered angle of the steered wheels according to a steering operation, and a reaction force actuator that applies a steering reaction force to the steering And a road surface reaction force detecting means for detecting a road surface reaction force acting on the steered wheels, and controlling the operation of the reaction force actuator to apply the steering reaction force according to the detected road surface reaction force to the steering wheel. A vehicle steering apparatus comprising a control means for
In the case where the application direction of the detected road surface reaction force is a direction to increase the turning angle, the control means is configured to make the applied steering reaction force constant at a value at the time of the detection. A vehicle steering apparatus characterized by controlling an operation of a force actuator. The vehicle steering apparatus according to claim 1,
The control means detects the steering reaction force to be applied when the detected application direction of the road surface reaction force is a direction in which the turning angle is decreased and the change speed is larger than a predetermined value. Controlling the operation of the reaction force actuator to be constant at the value at the time of
A vehicle steering apparatus characterized by the above. In the vehicle steering device according to claim 1 or 2,
The control means stores the value of the road surface reaction force at a time when the steering reaction force is constant, and the steering reaction force is increased until the detected current value of the road surface reaction force becomes equal to the stored value. A vehicle steering apparatus, wherein the operation of the reaction force actuator is controlled to be constant.

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