JP2006290135A - Steering control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the generation of a sense of incongruity in steering and a drop of the steering performance when a backup cable is elongated abnormally and to prevent the backup cable from accelerating in its deterioration. <P>SOLUTION: A steering control device is structured so that a steering part having a steering wheel 1 and a steering reaction force motor 3 and a wheel turning part having a front left 12a and a front right wheel 12b and a wheel turning motor 7 are separably coupled together through the backup cable mechanically, and is further equipped with a steering controlling means to conduct the SBW control through a wheel turning control and a steering reaction force control upon separating the steering part and the wheel turning part from each other and the EPS control to be made upon coupling the steering part with the wheel turning part through the backup cable 6, wherein the steering controlling means is arranged as refraining from executing the EPS control even if an abnormal elongation of the cable is judged when it is determined that it is possible to conduct the SBW control. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steer-by-wire system in which a steering unit having a steering wheel and a steering reaction force actuator and a steering unit having a steering wheel and a steering actuator can be mechanically separated and connected via a backup cable. It belongs to the technical field of steering control devices.

  Normally, the steering wheel and the steered wheel operate as a so-called steer-by-wire (hereinafter abbreviated as “SBW”), and the steering wheel and the steered wheel are mechanically connected in an abnormal state. A controller that has a mechanical backup cable to be operated in the vehicle, has a steering angle sensor and a steering angle sensor, has a steering reaction force motor and a steering motor, and calculates a steering reaction force command value and a steering command value And a system for driving each motor based on the steering reaction force command value and the steering command value is known (see, for example, Patent Document 1).

In this type of SBW system, if an abnormality is found in a part of the system, the backup wheel is quickly connected to mechanically connect the steering wheel and the steered wheel. Electric power steering (hereinafter abbreviated as “EPS”) has been controlled to prevent the vehicle from becoming heavy and to reduce the load on the driver.
JP 2002-225733 A

  However, in the conventional steering control device, when an abnormality is recognized in a part of the system during execution of SBW control, the steering wheel and the steering wheel are mechanically coupled by quickly connecting the backup clutch. However, since the “SBW control” is shifted to the “EPS control”, there are the following problems.

  If the backup cable continues to be used even when its extension exceeds the allowable amount due to deterioration over time, etc., it will be changed from SBW control to control using the backup cable due to some failure, that is, EPS control. In the case of a transition, due to the influence of this abnormal cable extension, on the steering side, even if the driver originally needs steering torque even when the steering torque is necessary, the torque is no longer needed, that is, in this area No reaction force is generated. On the other hand, since the EPS side performs “EPS control” based on the detected value of the steering torque sensor on the steered side, the actual torque is not generated on the steering side as described above. An area that does not move (dead zone) is generated. Furthermore, there is a problem that if the backup cable continues to be stressed by continuing to use the backup cable by “EPS control”, the backup cable promotes deterioration.

  The present invention has been made paying attention to the above problem, and can suppress the occurrence of a sense of incongruity and a decrease in the steering performance when the backup cable is abnormally stretched, and the steering that can prevent the deterioration of the backup cable. An object is to provide a control device.

In order to achieve the above object, in the present invention, a steering unit having a steering wheel and a steering reaction force actuator and a steering unit having a steering wheel and a steering actuator are mechanically separated and connected via a backup cable. Is possible,
Steer-by-wire control is performed by turning the steering unit and the steered unit, and turning the steering control to make a turning angle according to the steering state, and the steering reaction force control giving the steering reaction force according to the turning state. And steering control means for connecting the steering section and the steering section via the backup cable, and performing steering assist control using at least one of the steering reaction force actuator and the steering actuator as an assist means,
In a steering control device with
Steer-by-wire abnormality determining means for determining whether the steer-by-wire control is possible;
A cable extension amount detecting means for detecting a cable extension amount which is an extension of the backup cable;
When the cable extension amount is equal to or greater than a predetermined value, a cable abnormality determining means for determining that the cable is abnormal is provided,
When the steering control unit determines that the steer-by-wire control is possible by the steer-by-wire abnormality determination unit, the steering assist control is not executed even if the cable abnormality determination unit determines that the cable is abnormal. And

  Therefore, in the steering control device of the present invention, when the steering control means determines that the steer-by-wire control is possible by the steer-by-wire abnormality determination means, the cable abnormality determination means causes the cable extension amount to exceed a predetermined value. Even if it is determined that the cable is abnormal, the steering assist control is not executed. In other words, even if an elongation abnormality occurs in the backup cable, the steering assist control is performed by connecting the steering unit and the steering unit via the backup cable and using at least one of the steering reaction force actuator and the steering actuator as an assist means. Not executed. For this reason, for example, when a cable elongation abnormality is recognized, the steering reaction force is not generated due to the influence of cable elongation, as in the case where steering assist control is performed quickly, and the driver feels uncomfortable steering, It is possible to suppress the deterioration of the steering performance that there is a dead zone in which the steered wheels do not steer with respect to the driver's steering. Further, since the steering assist control is not executed, the use frequency of the backup cable can be lowered, and further deterioration of the backup cable can be prevented. As a result, when the backup cable is abnormally stretched, it is possible to suppress an uncomfortable feeling of steering and a decrease in steering performance, and it is possible to prevent the deterioration of the backup cable.

  Hereinafter, the best mode for carrying out the steering control device of the present invention will be described based on Examples 1 to 3 shown in the drawings.

First, the configuration will be described.
FIG. 1 is an overall configuration perspective view showing an SBW system to which the steering control device of the first embodiment is applied, and FIG. 2 is a control system block diagram of the SBW system to which the steering control device of the first embodiment is applied.
As shown in FIG. 1, the SBW system to which the steering control device of the first embodiment is applied includes a steering wheel 1 (handle), a torque sensor 2, a steering reaction force motor 3 (steering reaction force actuator), and a steering angle. Sensor 4, backup cable clutch 5, backup cable 6, steering motor 7 (steering actuator), steering angle sensor 8, steering reaction force controller 9, steering controller 10, and vehicle speed sensor 11 And a right front wheel 12a (steering wheel) and a left front wheel 12b (steering wheel).

  The steering part having the steering wheel 1 and the steering reaction motor 3 and the steering part having the left and right front wheels 12a and 12b and the steering motor 7 can be mechanically separated and connected via the backup cable 6. ing. When mechanically separating the steering portion and the steered portion, the backup cable clutch 5 is opened, and when the steering portion and the steered portion are mechanically coupled, the backup cable clutch 5 is fastened.

  Then, the steering portion and the turning portion are separated by releasing the backup cable clutch 5, and the turning control by the turning controller 10 with the turning angle corresponding to the steering state and the steering reaction corresponding to the turning state are performed. Steer-by-wire control (hereinafter abbreviated as “SBW control”) is performed by steering reaction force control by the steering reaction force controller 9 that applies force.

  Further, when “SBW control” is impossible and electric power steering control (hereinafter, abbreviated as “EPS control”) is possible, the backup cable clutch 5 is engaged to establish a backup cable. The steering unit and the steering unit are connected via 6 and “EPS control” (= steering assist control) is performed using at least one of the steering reaction force motor 4 and the steering motor 7 as an assist means.

  As shown in FIG. 2, the control system of the SBW system to which the steering control device of the first embodiment is applied is a steering reaction force motor angle sensor (= steering angle sensor 4), a vehicle speed as a sensor system for obtaining input information. A sensor 11 and a steering motor angle sensor (= steering angle sensor 8) are included.

  As a controller that performs arithmetic processing according to input information, a steering reaction force device controller (= steering reaction force controller 9) that inputs steering reaction force motor angle information and vehicle speed information, steering motor angle information, and vehicle speed. A steering device controller (= steering controller 10) for inputting information.

  The reaction force control during SBW control is the sum of the value obtained by multiplying the actual steering angle θs by the gain Ka and the value obtained by multiplying the actual steering angular velocity dθs / dt by the gain Ks, and the command turning angle θta Reaction torque according to the steered state of the left and right front wheels 12a, 12b by adding the value obtained by multiplying the deviation between the actual turning angle θt and the gain Kfa and the value obtained by multiplying the deviation differential value by the gain Kfs. Is set and a limiter process is performed to obtain a motor control command value Tms (see FIG. 6). Then, by a reaction force servo control by feedforward control + feedback control + robust compensation, a command current is obtained from the motor control command value Tms, and the steering reaction force motor 3 is driven.

  The steering control during the “SBW control” is, for example, an actual steering angle θta obtained by multiplying the actual steering angle θs by a gear ratio G set according to the vehicle speed or the like, and the actual steering angle θ obtained from the rotation angle of the steering motor 7. The deviation from the turning angle θt is converted into turning torque, and a limiter process is performed to obtain a motor control command value. Then, by turning servo control by feedforward control + feedback control + robust compensation, the command current Ita is obtained from the motor control command value, and the turning motor 7 is driven (see FIG. 7).

  The steering reaction force device controller includes a cable extension amount calculating means, a cable tension estimating means, a motor control command value calculating means, a motor driving means, a command turning angle calculating means, a steering reaction force motor. Thermal load calculation means. The steering device controller includes cable extension amount calculation means, cable tension estimation means, motor control command value calculation means, motor drive means, and steered motor thermal load calculation means. .

  The actuator that performs a control operation in accordance with a command from the controller is driven by the steering reaction force actuator (= steering reaction force motor 3) driven by the steering reaction force device controller and the steering device controller. A steering actuator (= steering motor 7).

Next, the operation will be described.
[Steering control processing]
FIG. 3 is a flowchart showing the flow of the steering control process executed by the controllers 9 and 10 of the first embodiment. Each step will be described below. This process is executed at a predetermined control cycle (for example, 10 msec) (steering control means).

In step S1, it is determined whether or not “SBW control” is possible in the existing system. If YES, the process proceeds to step S2, and if NO, the process proceeds to step S8 (steer-by-wire abnormality determination unit).
That is, if “SBW control” is possible even if an abnormality occurs in a part of the steer-by-wire system, the process proceeds to step S2.

In step S2, following the determination that “SBW control” is possible in step S1, the cable extension amount Sc of the backup cable 6 is detected (cable extension amount detection means), this is read, and the process proceeds to step S3.
Here, “detection of the cable extension amount Sc”, for example, causes the steering wheel 1 to rotate by passing a current through the steering reaction force motor 3 while the backup cable clutch 5 is engaged. And the angle of the steering wheel 1 when the electric current which flows into the steering reaction force motor 3 exceeds a certain threshold value is measured. This is measured in each of the left / right rotations, and a value obtained by multiplying the difference value of the measured angles by the cable extension amount conversion gain Kc is detected as the cable extension amount Sc of the backup cable 6.

In step S3, following the reading of the cable extension amount Sc in step S2, it is determined whether or not the cable extension amount Sc is equal to or greater than a predetermined value Sca, and if YES, the process proceeds to step S4. If NO, the process proceeds to step S5 (cable abnormality determining means).
Here, the “predetermined value Sca” is a value determined in advance in consideration of a looseness at the time of initial assembly, a durability test, and the like, and is set to 6 mm, for example.

  In step S4, following the determination that the cable extension amount is abnormal in step S3, a warning lamp (notification means) (not shown) is turned on, and the process proceeds to step S5.

  In step S5, following the determination that the cable extension amount is normal in step S3 or lighting of the warning lamp in step S4, the backup cable clutch 5 is released (the steering unit and the steering unit are mechanically connected). If YES, the process proceeds to step S7. If NO, the process proceeds to step S6.

  In step S6, following the determination that the backup cable clutch 5 is engaged in step S5, the backup cable clutch 5 is released in order to break the mechanical connection between the steering unit and the steered unit, and the process proceeds to step S7. Transition.

  In step S7, following the determination that the backup cable clutch 5 is disengaged in step S5 or the disengagement of the backup cable clutch 5 in step S6, the steering unit and the steering unit are mechanically separated. In this state, “SBW control” is performed to drive the steering reaction force motor 3 and the steered motor 7 based on the command values calculated on the steering side and the steered side, respectively.

  In step S8, following the determination that “SBW control” is not possible in the existing system in step S1, it is determined whether “EPS control” is possible. If YES, the process proceeds to step S9. If NO, the process proceeds to step S10.

  In step S9, following the determination that "EPS control" is possible in step S8, the backup cable clutch 5 is engaged, and the "EPS control" is performed in a state where the steering portion and the steered portion are mechanically coupled. And proceed to return.

  In step S10, following the determination that “EPS control” is impossible in step S8, the backup cable clutch 5 is engaged, and the control is stopped in a state where the steering unit and the steering unit are mechanically coupled. Then, a direct-coupled steering system with no assist is made, and a return is made.

[Steering control switching action]
When “SBW control” is possible and the cable extension amount Sc is normal, the flow of step S1, step S2, step S3, step S5, step S7, and return is repeated in the flowchart of FIG. Then, with the backup cable clutch 5 left open, the steering control for outputting a control command for obtaining a turning angle corresponding to the steering state of the steering wheel 1 to the steering motor 7, and the left and right front wheels 12a, 12b Ordinary “SBW control” is executed by steering reaction force control that outputs a control command for applying steering reaction force torque to the steering reaction force motor 3 in accordance with the steered state.

  Then, although “SBW control” is possible, if it is determined that the cable extension amount Sc is abnormally extended, in the flowchart of FIG. 3, step S1, step S2, step S4, step S5, step S6, and step S6. The flow from step S7 to return is repeated, the warning lamp is turned on in step S4, and the driver is informed of the cable extension abnormality. In step S7, regardless of the cable extension abnormality, “EPS control” is entered. Without switching, the normal “SBW control” is continuously executed as it is.

  If it is determined that “SBW control” is not possible but “EPS control” is possible, the process proceeds from step S1 to step S8 to step S9 in the flowchart of FIG. 3, and backup is performed in step S9. The cable clutch 5 is engaged and switched from “SBW control” to “EPS control”. Thereafter, “EPS control” is maintained as it is unless the determination condition is changed.

  Further, if it is determined that “SBW control” is not possible and “EPS control” is also impossible, the process proceeds from step S1 to step S8 to step S10 in the flowchart of FIG. The backup cable clutch 5 is engaged, both “SBW control” and “EPS control” are stopped, and the steering mode is switched to the direct connection steering mode in which the steering wheel 1 and the left and right front wheels 12a and 12b are directly connected. In this direct-coupled steering mode, assist force cannot be obtained unlike "EPS control", but it is guaranteed that the left and right front wheels 12a and 12b are steered only by the steering force applied to the steering wheel 1.

[Steering control action]
In the steering control device of the first embodiment, for example, during “SBW control”, when it is determined in step S1 that “SBW control” is possible, even if it is determined in step S3 that the cable extension is abnormal, From step S3 to step S4 → step S5 → step S7, the “SBW control” is maintained as it is. That is, even if an elongation abnormality occurs in the backup cable 6, the steering unit and the turning unit are connected via the backup cable 6, and at least one of the steering reaction force motor 3 and the turning motor 7 is used as an assist means. “EPS control” is not executed.

  For example, when the backup cable 6 continues to be used with its elongation exceeding the allowable amount due to deterioration over time, etc., when the switch is made from “SBW control” to “EPS control” or during the “SBW control” When the shift to EPS control is promptly made due to an abnormality, the torque on the steering side when the driver is steering and the cable is slack even when the steering torque is originally required due to the influence of cable elongation. Is no longer necessary, that is, no reaction force is generated in this region. On the other hand, since the EPS side performs “EPS control” based on the detected value of the steering torque sensor on the steered side, the actual torque is not generated on the steering side as described above. An area that does not move (dead zone) is generated. Further, by continuing to use this backup cable by “EPS control”, if the backup cable continues to be stressed, the backup cable promotes deterioration.

On the other hand, in the first embodiment, since “EPS control” is not executed when the back-up cable 6 is abnormally stretched, the steering reaction force is not generated, thereby giving the driver a feeling of steering discomfort, It is possible to suppress the occurrence of deterioration of the steering performance in which there is a dead zone where the steered wheels do not steer.
In addition, if the backup cable 6 is abnormally stretched, “EPS control” is not executed, so the frequency of use of the backup cable 6 can be reduced compared to switching to “EPS control” and further deterioration of the backup cable 6 is prevented. it can.
In addition, when an abnormality occurs in the backup cable 6, a warning lamp is turned on and a warning is issued to the driver. Therefore, the vehicle can be quickly taken to the dealer or the like to prompt the user to replace or repair the backup cable 6.
In addition, if an abnormal expansion occurs in the backup cable 6, normal “SBW control” is executed instead of “EPS control”, so the steering gear ratio can be set freely by setting the control law in “SBW control”. The degree of freedom is also improved.

Next, the effect will be described.
In the steering control device of the first embodiment, the effects listed below can be obtained.

  (1) The steering part having the steering wheel 1 and the steering reaction motor 3 and the steering part having the left and right front wheels 12a and 12b and the steering motor 7 can be mechanically separated and connected via the backup cable 6. The steering unit and the steered unit are separated from each other, and the steering control that makes the steering angle according to the steering state and the steering reaction force control that gives the steering reaction force according to the steering state “SBW control” is performed, and the steering unit and the steered unit are connected via the backup cable 6, and at least one of the steering reaction force motor 3 and the steered motor 7 is used as an assisting unit. In the steering control device, the steer-by-wire abnormality determining means (step S1) for determining whether or not the “SBW control” is possible, and the extension of the backup cable 6. A cable extension amount detecting means (step S2) for detecting the cable extension amount Sc; a cable abnormality determining means (step S3) for determining that the cable is abnormal when the cable extension amount Sc is equal to or greater than a predetermined value Sca; When the steering control means determines that the “SBW control” is possible by the steer-by-wire abnormality determination means, the steering control means performs the “EPS control” even if the cable abnormality determination means determines that the cable is abnormal. Since it is not executed, when the backup cable 6 is abnormally stretched, it is possible to suppress an uncomfortable feeling of steering and a decrease in the steering performance, and it is possible to prevent the deterioration of the backup cable 6.

  (2) The steering control means executes the “SBW control” in which the steering unit and the steered unit are separated when a cable abnormality is determined during the determination that the “SBW control” is possible. The degree of freedom in steering control can be improved compared to the case where “EPS control” is executed, such as setting the steering gear ratio freely.

  (3) A warning lamp (notification means) for notifying the driver of abnormality in the steering control system is provided, and the steering control means notifies the abnormality with the warning lamp when the cable abnormality determination means determines that the cable is abnormal. Therefore, it is possible to promptly bring the vehicle to a dealer or the like and prompt the user to replace or repair the backup cable 6.

  In the second embodiment, when a cable abnormality is determined while it is determined that “SBW control” is possible, the steering unit and the steered unit are mechanically coupled, and the mechanical unit between the steered unit and the steered unit is mechanically connected. This is an example in which a fixed gear ratio steer-by-wire control (hereinafter, abbreviated as “fixed gear ratio SBW control”) for maintaining an appropriate gear ratio is executed. Since the configuration is the same as that of the first embodiment shown in FIGS. 1 and 2, illustration and description thereof are omitted.

Next, the operation will be described.
[Steering control processing]
FIG. 4 is a flowchart showing the flow of the steering control process executed by the controllers 9 and 10 of the second embodiment. Hereinafter, each step will be described (steering control means). Steps S21 to S24 correspond to Steps 1 to S4 in FIG. 3, respectively, and Steps S28 to S30 correspond to Steps S8 to S10 in FIG.

  In step S25, following the lighting of the warning lamp in step S24, it is determined whether or not the backup cable clutch 5 is engaged (the steering unit and the steered unit are mechanically coupled). If YES, the process proceeds to step S27. If NO, the process proceeds to step S26.

  In step S26, following the determination that the backup cable clutch 5 is disengaged in step S25, the backup cable clutch 5 is engaged to mechanically connect the steering unit and the steered unit, and the process proceeds to step S27. Transition.

  In step S27, following the determination that the backup cable clutch 5 is engaged in step S25 or the engagement of the backup cable clutch 5 in step S26, the steering unit and the steering unit are mechanically coupled. In the state, “fixed gear ratio SBW control” is performed to maintain the mechanical gear ratio (= 1) between the steering unit and the steered unit, and the process proceeds to return.

  In step S31, following the determination that the cable extension amount is normal in step S23, it is determined whether or not the backup cable clutch 5 is disengaged (the steering unit and the steered unit are not mechanically connected). If so, the process proceeds to step S33. If NO, the process proceeds to step S32.

  In step S32, following the determination that the backup cable clutch 5 is engaged in step S5, the backup cable clutch 5 is released in order to break the mechanical connection between the steering unit and the steered unit, and the process proceeds to step S33. Transition.

  In step S33, following the determination that the backup cable clutch 5 is disengaged in step S31 or the disengagement of the backup cable clutch 5 in step S32, the steering section and the steering section are mechanically disconnected. In this state, normal “SBW control” for driving the steering reaction force motor 3 and the steered motor 7 is performed based on the command values calculated on the steering side and the steered side, respectively, and the process proceeds to return.

[Fixed gear ratio SBW control processing]
FIG. 5 is a flowchart showing a flow of a fixed gear ratio SBW control process executed after switching to “fixed gear ratio SBW control” (step S27 in FIG. 4) by the controllers 9 and 10 of the second embodiment. Each step will be described.

In step S27-1, the vehicle speed V, the actual steering angle θs, the actual turning angle θt, the steering motor thermal load value Tls, and the steering motor thermal load value Tlt are read, and the process proceeds to step S27-2.
Here, the vehicle speed V is obtained from the vehicle speed sensor 11, the actual steering angle θs is obtained from the steering angle sensor 4, the actual turning angle θt is obtained from the turning angle sensor 8, and the steering motor thermal load value Tls is obtained from the steering reaction. It is read from the force motor thermal load calculation means (actuator usage frequency equivalent value detection means), and the turning motor thermal load value Tlt is read from the steering motor thermal load calculation means (actuator usage frequency equivalent value detection means). The thermal load value of the steering reaction motor 3 and the thermal load value of the steering motor 7 are, for example, the amount of heat generated by each of the motors 3 and 7 within a predetermined time Tp (for example, 10 minutes) that goes back from the present to the past. To do.

In step S27-2, following the acquisition of the input information in step S27-1, the magnitude of the steering reaction torque and the steering are calculated from the cable extension amount Sc, the steering motor thermal load value Tls, and the steered motor thermal load value Tlt. The degree of control follow-up is determined and the process proceeds to step S27-3.
That is, as the cable extension amount Sc is smaller, the torque output from the steering reaction force motor 3 is increased and the control followability of the steered motor 7 is increased, and the steering motor thermal load value Tls and the steered motor thermal load value Tlt are increased. Accordingly, the loads of the motors 3 and 7 are determined so that the load is not biased to one of the motors. For example, when the steering motor thermal load value Tls of the steering reaction force motor 3 is high, the ratio for increasing the magnitude of the steering reaction force torque is decreased, and the ratio for increasing the tracking control followability is increased. Conversely, when the steered motor thermal load value Tlt of the steered motor 7 is high, the ratio for increasing the magnitude of the steering reaction torque is increased, and the ratio for increasing the followability of the steering control is decreased.

In step S27-3, following the determination of the magnitude of the steering reaction torque in step S27-2 and the degree of increase in the followability of the turning control, the actual steering angle θs and the actual turning angle θt are calculated from the cable extension amount Sc. A value Scd obtained by subtracting the product of the cable expansion amount conversion gain Kc and the absolute value of the difference is calculated, and the process proceeds to step S27-4 (corresponding to cable tension estimating means).
The command turning angle θta in this case is equal to the actual steering angle θs because the control is performed with a gear ratio of 1. Therefore, basically, the actual turning angle θ follows the actual steering angle θ. The calculation formula for the value Scd is
Scd = Sc−Kc ・ (| θs−θt |)
It becomes.

In step S27-4, following the calculation of the value Scd in step S27-3, it is determined whether or not the value Scd is equal to or smaller than a predetermined value Sct. If YES, the process proceeds to step S27-5. If NO, the process moves to step S27-8.
Here, the “predetermined value Sct” is a value that slightly tensions the backup cable 6, in other words, a value that causes a control delay due to the tension. For example, the amount of elongation with respect to 10N (10 / Kt) And However, Kt is a gain [N / m] for converting the elongation amount into the tension. Instead of calculating the value Scd, the tension of the backup cable 6 may be directly detected.

  In step S27-5, following the determination that the value Scd in step S27-4 is equal to or less than the predetermined value Sct, it is determined whether or not the vehicle speed V is zero (vehicle stop). If YES, step S27 is determined. -6. If NO, the process moves to step S27-8.

In step S27-6, following the determination that the vehicle speed V = 0 in step S27-5, the backup cable clutch 5 is released, and the process proceeds to step S27-7.
Here, the backup cable clutch 5 is released because the Scd ≦ Sct condition in step S27-4 and the V = 0 condition in step S27-5 are both satisfied, so that the backup cable is maintained while maintaining safety. The purpose is to prevent 6 from being stressed. It should be noted that instead of the condition of V = 0, it is also possible to use a condition with little influence of delay at the time of backup transition, such as when the steering angle is neutral or when the steering angular velocity is approximately zero.

  In step S27-7, following the release of the backup cable clutch 5 in step S27-6, the normal motors 7 and 7 are driven based on the command values calculated on the steering side and the steered side. Perform “SBW control” and return to step S27-1.

  In step S27-8, following the determination that the value Scd in step S27-4 exceeds the predetermined value Sct, it is determined whether the backup cable clutch 5 is engaged or not. Then, the “fixed gear ratio SBW control” is continued. If NO, the process moves to step S27-9.

  In step S27-9, following the determination that the backup cable clutch 5 is disengaged in step S27-8, it is determined whether or not there is an angular misalignment (= N misalignment) between steering / steering. If YES, the process proceeds to step S27-10, and if NO, the process proceeds to step S27-11.

  In step S27-10, following the determination of the presence of N deviation in step S27-9, each motor 3, based on the command values calculated on the steering side and the steered side so as to perform N deviation correction. “SBW control” for driving 7 is performed, and the process proceeds to step S27-11.

  In step S27-11, following the determination that there is no N deviation in step S27-9 or the N deviation correction in step S27-10, the backup cable clutch 5 is engaged, and “fixed gear ratio SBW control” is performed. And go to return.

[Steering control switching action]
When “SBW control” is possible and the cable extension amount Sc is also normal, in the flowchart of FIG. 4, the flow proceeds from step S21 → step S22 → step S23 → step S31 → (step S32 →) step S33 → return. Repeatedly, in step S33, the steering control for outputting to the steering motor 7 a control command for obtaining a turning angle corresponding to the steering state of the steering wheel 1 with the backup cable clutch 5 opened, Ordinary “SBW control” is executed by steering reaction force control for outputting a control command for applying a steering reaction force torque to the steering reaction force motor 3 in accordance with the steering state of the front wheels 12a and 12b.

  Then, although “SBW control” is possible, if it is determined that the cable extension amount Sc is abnormally extended, in the flowchart of FIG. 4, step S21 → step S22 → step S23 → step S24 → step S25 → (step S26 →) Step S27 → Return is repeated, the warning lamp is turned on in step S24, and the driver is informed of cable extension abnormality. In step S27, “EPS Without switching to “control”, “fixed gear ratio SBW control” is performed in which the gear ratio is set to 1 and the steering control and the steering reaction force control are performed.

  If it is determined that “SBW control” is not possible but “EPS control” is possible, in the flowchart of FIG. 4, the process proceeds from step S21 to step S28 to step S29, and backup is performed in step S29. The cable clutch 5 is engaged and switched from “SBW control” to “EPS control”. Thereafter, “EPS control” is maintained as it is unless the determination condition is changed.

  Furthermore, if it is determined that “SBW control” is not possible and “EPS control” is not possible, the process proceeds from step S21 to step S28 to step S30 in the flowchart of FIG. The backup cable clutch 5 is engaged, both “SBW control” and “EPS control” are stopped, and the steering mode is switched to the direct connection steering mode in which the steering wheel 1 and the left and right front wheels 12a and 12b are directly connected. In this direct-coupled steering mode, assist force cannot be obtained unlike "EPS control", but it is guaranteed that the left and right front wheels 12a and 12b are steered only by the steering force applied to the steering wheel 1.

[Steering control action]
In the steering control device according to the second embodiment, for example, during “SBW control”, when it is determined in step S21 that “SBW control” is possible, even if it is determined in step S23 that the cable extension is abnormal, The process proceeds from step S23 to step S24 → step S25 → step S26 → step S27, where “SBW control” is switched to “fixed gear ratio SBW control”.

  That is, even if an elongation abnormality occurs in the backup cable 6, the steering unit and the turning unit are connected via the backup cable 6, and at least one of the steering reaction force motor 3 and the turning motor 7 is used as an assist means. By not performing “EPS control”, as described in the first embodiment, it is possible to suppress the occurrence of an uncomfortable feeling of steering and a decrease in steering performance when the backup cable 6 is abnormally stretched.

  In addition, in the “fixed gear ratio SBW control”, by connecting the backup cable clutch 5 in advance, it is not necessary to connect the backup cable clutch 5 when a secondary failure occurs. And the fluctuation at the time of secondary failure can be minimized.

  In the “fixed gear ratio SBW control”, the backup cable clutch 5 is connected, but the extension amount of the backup cable 6 exceeds an allowable value, that is, the backup cable 6 has a corresponding slack. Even if the “fixed gear ratio SBW control” is performed, the back-up cable 6 is hardly stressed due to the slack, and therefore the deterioration of the back-up cable 6 (further increase in the amount of elongation, etc.) can be prevented.

[Fixed gear ratio SBW control action]
In the “fixed gear ratio SBW control”, since the cable extension amount Sc is known, the process proceeds from step S27-1 to step S27-2 in the flowchart of FIG. 5, and in step S27-2, the smaller the cable extension amount Sc is, In addition, the torque output from the steering reaction motor 3 is increased and the control followability of the steered motor 7 is increased.

  That is, as the cable extension amount Sc is smaller, the sag of the backup cable 6 is smaller, and the allowable value that does not hinder the control between the steering side and the steered side is smaller. By increasing the command reaction torque on the steering reaction force side to suppress the steering speed, the turning angle can follow the steering angle. As a result, the difference between the steering angle and the turning angle can be reduced, and the frequency with which the backup cable 6 is stressed can be reduced.

Here, the command reaction force torque on the steering reaction force side is obtained by multiplying the actual steering angle θs and its time differential value ωs (= dθs / dt) by gains Ka and Ks corresponding to the vehicle speed, respectively, as shown in FIG. The sum is Ts (Ts = Ka × θs + Ks × ωs).
Further, the deviation (θta−θt) between the command turning angle θta calculated by the steering reaction force controller and the actual turning angle θt read from the turning device controller, and the time differential value (= d (θta Multiply -θt) / dt by gains Kfa and Kfs according to the vehicle speed, and add them to obtain Tts (Tts = Kfa × (θta−θt) + Kfs × ωts).
Tsa (= Ts + Tts + Tmc) is obtained by adding the steering reaction force correction value Tmc to the sum of Ts and Tts. The limit value Ls obtained from the road surface μ estimated from the vehicle speed, the yaw rate, the lateral acceleration, etc. is subjected to a limiter process, and this is used as the steering reaction force command value Tms.
This prevents the reaction force from becoming too large when the steering angle or the steering angular acceleration is increased, prevents the steering wheel 1 from being increased or not easily increased, and depends on the vehicle characteristics. The steering reaction force can be changed. Then, the steering wheel 1 can be made difficult to intentionally increase by adding a steering reaction force correction value Tmc having a larger value as the cable extension amount Sc is smaller.

  In addition, as shown in the turning angle control block employing the robust matching method in FIG. 7, the followability of the turning control is provided with a variable limiter for the output Ir for the calculated disturbance compensation, and this limiter value is raised or lowered. In this way, the followability of the turning control is raised and lowered. For example, if the limit value is increased as the cable extension amount Sc is smaller, the amount of disturbance compensation increases, and the follow-up performance increases.

  Further, as described above, when the cable elongation amount Sc is smaller, the torque output from the steering reaction motor 3 is increased and the control followability of the steered motor 7 is increased. In the flowchart of FIG. 1 → Proceed to step S27-2. In step S27-2, depending on the use frequency of the steering side / steering side motor (the steering motor thermal load value Tls and the steering motor thermal load value Tlt at a certain time), The degree of increasing the torque output from the steering reaction motor 3 and the degree of increasing the control followability of the turning motor 7 are determined.

  Therefore, since the load is not biased to either one of the steering reaction force motor 3 and the steering motor 7, it is possible to suppress the steering reaction force motor 3 and the steering motor 7 from being overheated.

  In addition, as the cable extension amount Sc is smaller, the torque output from the steering reaction force motor 3 is increased and the control followability of the steered motor 7 is increased, and the steering motor thermal load value Tls and the steered motor thermal load value are increased. When determining the degree of increasing the torque output from the steering reaction force motor 3 and the degree of increasing the control followability of the steered motor 7 according to Tlt, in the flowchart of FIG. 5, step S27-1 → step S27- 2 → Proceed to step S27-3. In step S27-3, a value Scd (= Sc−Kc · (| θs−θt |)) is calculated. When the value Scd is equal to or less than the set value Sct and the vehicle speed V is zero, in the flowchart of FIG. 5, from step S27-3 to step S27-4 → step S27-5 → step S27-6 → step S27− Proceed to 7 to release the backup cable clutch 5 and perform “SBW control”. When “SBW control” is entered, but Scd ≦ Sct and the vehicle speed V ≠ 0, or Scd> Sct, step S27-4 or step S27-4 in the flowchart of FIG. From S27-5 to step S27-8 → step S27-9 → (step S27-10 →) proceed to step S27-11, the N shift is corrected as necessary, and the backup cable clutch 5 is again engaged and “ Fixed gear ratio SBW control ”.

  That is, when the driver steers in a situation where the turning side cannot physically increase further, such as a curbstone, and a difference greater than the extension amount of the backup cable 6 occurs between the steering part and the turning part. If the backup cable 6 is stretched, the backup cable 6 is further stressed.

  Therefore, the backup cable is used only when the vehicle speed V is zero and the value Scd obtained by subtracting the difference between the steering angle and the turning angle from the cable extension amount Sc is smaller than the predetermined set value Sct. By disengaging the clutch 5, the driver steers in a situation where the left and right front wheels 12a, 12b are in contact with the curb, etc., and a difference greater than the extension amount of the backup cable 6 occurs between the steering part and the steered part. However, since the backup cable 6 is not stretched due to the escape due to the clutch being released, it is possible to prevent the backup cable 6 from being further stressed. Incidentally, in FIG. 8, the left and right front wheels 12a and 12b contact the curbstone, the followability between the actual steering angle θs and the actual turning angle θt is solved, and the transition starts with the actual turning angle θt remaining at a fixed value of θt1. 6 is a time chart when the backup cable clutch 5 is disengaged at a time t1 when the steering angle deviation θtd (= θs1−θt1) exceeds a set value.

  Further, if the condition of Scd ≦ Sct and the vehicle speed V = 0 is satisfied, even if a secondary failure occurs with the backup cable clutch 5 opened, the vehicle is in a stopped state, so safety is maintained. . In addition, since a plurality of conditions for releasing the backup cable clutch 5 are provided, it is not necessary to frequently connect or disengage the backup cable clutch 5, and it is possible to suppress the occurrence of N deviation as much as possible.

Next, the effect will be described.
In the steering control device of the second embodiment, in addition to the effects (1) and (3) of the first embodiment, the effects listed below can be obtained.

  (4) When a cable abnormality is determined during the determination that the “SBW control” is possible, the steering control unit mechanically connects the steering unit and the steered unit by the backup cable 6; In order to execute the “fixed gear ratio SBW control” that maintains the mechanical gear ratio between the steering unit and the steered unit, it is possible to minimize fluctuations at the time of secondary failure, and to perform backup. Deterioration due to further increase in the amount of extension of the cable 6 can also be prevented.

  (5) When executing the “fixed gear ratio SBW control”, the steering control means increases the torque output from the steering reaction force motor 3 as the cable extension amount Sc decreases, and the steering motor. In order to improve the control followability of No. 7, when the cable extension amount Sc is small, that is, when the allowable value that does not hinder the control between the steering side and the steered side is small, the difference between the steering angle and the steered angle is kept small. By doing so, it is possible to reduce the frequency with which the backup cable 6 is stressed.

  (6) The thermal load value Tls of the steering reaction motor 3 and the thermal load value Tlt of the steered motor 7 are calculated, and when the steering control means executes the “fixed gear ratio SBW control”, the cable extension The smaller the amount Sc, the larger the torque output from the steering reaction motor 3 and the control followability of the steered motor 7, and the steering reaction force motor thermal load value Tls and the steered motor thermal load. Since the loads of the motors 3 and 7 are determined according to the value Tlt so that the load is not biased to one of the motors, it is possible to suppress one of the motors 3 and 7 from being overheated.

  (7) Cable tension estimation means for estimating the tension of the backup cable 6 is provided, and the steering control means determines that the SBW when the estimated cable tension is not less than a predetermined value during the “fixed gear ratio SBW control”. After executing the control and correcting the angular position deviation due to the difference between the steering angle and the turning angle, the steering portion and the turning portion are mechanically connected again by the backup cable 6, and the "fixed gear" Because the ratio SBW control is executed, even if the backup cable 6 is stretched during the fixed gear ratio SBW control, the tension can be quickly eliminated, and further stress can be prevented from being applied to the backup cable 6 and the secondary loss can be prevented. Safety is maintained even if a fault occurs.

  In the third embodiment, when a cable abnormality is determined during the determination that “SBW control” is possible, the steering unit and the steered unit are mechanically coupled to each other, and the mechanical unit between the steering unit and the steered unit is mechanically connected. This is an example in which the cable tension is estimated when executing the “fixed gear ratio SBW control” for maintaining a proper gear ratio, and self-steer is prevented when the cable is tensioned. Since the configuration is the same as that of the first embodiment shown in FIGS. 1 and 2, illustration and description thereof are omitted.

Next, the operation will be described.
[Fixed gear ratio SBW control processing]
FIG. 9 is a flowchart showing the flow of the fixed gear ratio SBW control process executed after switching to “fixed gear ratio SBW control” (step S27 in FIG. 4) by the controllers 9 and 10 of the third embodiment. Each step will be described. The basic control is executed according to the flowchart shown in FIG.

In step S27-21, the tension Tc of the backup cable 6 estimated by the cable tension estimating means is read, and the process proceeds to step S27-22.
Here, the “tension Tc of the backup cable 6” is obtained by multiplying the cable elongation amount Sc by, for example, multiplying the absolute value of the difference between the actual steering angle θs and the actual turning angle θt by the cable elongation amount conversion gain Kc. It is estimated by multiplying the subtracted value Std (= Kc · | θs−θt | −Sc) by the tension conversion gain Kt (Tc = Std · Kt).

  In step S27-22, following the reading of the cable tension Tc in step S27-21, the read tension Tc of the backup cable 6 is a predetermined value Tca (a value that slightly tensions the backup cable 6). For example, it is determined whether or not 10N) or more. If YES, the process proceeds to step S27-23, and if NO, the process proceeds to return (continuation of “fixed gear ratio SBW control”).

In step S27-23, following the determination that the cable tension Tc in step S27-22 is equal to or greater than the predetermined value Tca, the steering reaction torque is increased, the followability of the steering control is reduced, and the command turning angle is set. Change to perform at least one of the three, and move to return.
Here, “increasing the steering reaction torque” is as described in the second embodiment with reference to FIG. Further, “decreasing the followability of the steering control” is as described based on FIG. 7 in the second embodiment. Furthermore, “decreasing the command turning angle” means obtaining a command turning angle correction amount θtac that increases as the cable tension Tc increases in a region where the cable tension Tc is equal to or greater than a predetermined value Tca, as shown in FIG. Then, the command turning angle is lowered by subtracting the command turning angle correction amount θtac from the normal command turning angle.

[Fixed gear ratio SBW control action]
In the “fixed gear ratio SBW control”, the steering side and the steered side are combined, and the fact that the tension Tc of the backup cable 6 is equal to or greater than the predetermined value Tca means that the steering side and the steered side are strong. It will be in a conclusion state. For this reason, if the same control as usual is performed on the steering motor 7 in this state, the steering side moves due to the movement of the steering side, and the command turning angle is determined by the movement of the steering side, due to the high followability. There is a possibility that the steering side will move repeatedly and change, that is, self-steering.

  On the other hand, in Example 3, when the tension Tc of the backup cable 6 is equal to or greater than the predetermined value Tca, the followability of the control on the turning side is reduced, or the command turning used for turning control is performed. Decrease the angle from the normal value to suppress further movement on the steered side, or increase the reaction torque on the steering reaction force side to be larger than normal, and use it in the direction of further increase due to the above-mentioned influence. By suppressing this, self-steering can be prevented even when tension is applied to the backup cable 6.

Next, the effect will be described.
In the steering control device of the third embodiment, in addition to the effects (1) and (3) of the first embodiment and the effect (4) of the second embodiment, the following effects can be obtained.

  (8) Cable tension estimation means for estimating the tension of the backup cable 6 is provided, and when the steering control means executes the “fixed gear ratio SBW control”, the estimated cable tension Tc is equal to or greater than a predetermined value Tca. In this case, the control followability of the steering motor 7 is lowered, the value of the command turning angle used for the turning control is made smaller than usual, or the torque output from the steering reaction force motor 3 is made larger than usual. Since at least one of the three is performed, self-steering can be prevented even when the backup cable 6 is tensioned.

  As mentioned above, although the steering control apparatus of this invention has been demonstrated based on Example 1-3, it is not restricted to these Examples about a concrete structure, Each claim of a claim is a claim. Design changes and additions are allowed without departing from the gist of the invention.

  In the first embodiment, an example of steering control means that continues “SBW control” when it is determined that “SBW control” is possible and it is determined that the cable extension is abnormal is shown. The example of the steering control means that switches to `` fixed gear ratio SBW control '' when it is determined that `` SBW control '' is possible and it is determined that the cable extension is abnormal has been shown. If it is determined that the cable extension is possible, even if it is determined that the cable extension is abnormal, “EPS control” that stresses the backup cable is not executed, and switching to control other than the embodiment is also included.

  In the first to third embodiments, an example of a steering control device applied to a steer-by-wire system using a backup cable and a backup cable clutch as a backup means has been described. It can be applied to other steer-by-wire systems.

1 is an overall configuration diagram illustrating a steer-by-wire system to which a steering control device according to a first embodiment is applied. It is a control block diagram of a steer-by-wire system to which the steering control device of the first embodiment is applied. 3 is a flowchart showing a flow of steering control processing executed by the controller of Embodiment 1; 6 is a flowchart illustrating a flow of a steering control process executed by a controller according to a second embodiment. 12 is a flowchart illustrating a flow of a fixed gear ratio SBW control process executed after switching to “fixed gear ratio SBW control” by the controller of the second embodiment. FIG. 6 is a steering reaction force control block diagram at the time of “SBW control” and “fixed gear ratio SBW control” by the steering reaction force device controller of the second embodiment. FIG. 10 is a block diagram illustrating a turning angle control at the time of “SBW control” and “fixed gear ratio SBW control” by the steering device controller according to the second embodiment. 6 is a time chart showing an example when the backup clutch is turned off when the vehicle speed is zero in the steering control device of the second embodiment. 12 is a flowchart showing a flow of a fixed gear ratio SBW control process executed after switching to “fixed gear ratio SBW control” by the controller of the third embodiment. It is a map characteristic figure which shows the relationship of the command turning angle correction amount with respect to the cable tension used by fixed gear ratio SBW control of Example 3. FIG.

Explanation of symbols

1 Steering wheel (handle)
2 Torque sensor 3 Steering reaction force motor (steering reaction force actuator)
4 Steering angle sensor 5 Backup cable clutch 6 Backup cable 7 Steering motor (steering actuator)
8 Steering angle sensor 9 Steering reaction force controller 10 Steering controller 11 Vehicle speed sensor 12a Right front wheel (steering wheel)
12b Front left wheel (steering wheel)

Claims (9)

A steering part having a steering wheel and a steering reaction force actuator, and a steering part having a steering wheel and a steering actuator can be mechanically separated and connected via a backup cable.
Steer-by-wire control is performed by turning the steering unit and the steered unit, and turning the steering control to make a turning angle according to the steering state, and the steering reaction force control giving the steering reaction force according to the turning state. And steering control means for connecting the steering section and the steering section via the backup cable, and performing steering assist control using at least one of the steering reaction force actuator and the steering actuator as an assist means,
In a steering control device with
Steer-by-wire abnormality determining means for determining whether the steer-by-wire control is possible;
A cable extension amount detecting means for detecting a cable extension amount which is an extension of the backup cable;
When the cable extension amount is equal to or greater than a predetermined value, a cable abnormality determining means for determining that the cable is abnormal is provided,
The steering control means does not execute the steering assist control even when the cable abnormality determination means determines that the cable is abnormal when the steer-by-wire abnormality determination means determines that the steer-by-wire control is possible. A steering control device. In the steering control device according to claim 1,
The steering control means performs the steer-by-wire control in which the steering unit and the steered unit are separated when a cable abnormality is determined during the determination that the steer-by-wire control is possible. Control device. In the steering control device according to claim 1,
The steering control means mechanically connects the steering unit and the steered unit by the backup cable when a cable abnormality is determined during the determination that the steer-by-wire control is possible, and the steering unit and the steering unit A steering control device that performs a fixed gear ratio steer-by-wire control that maintains a mechanical gear ratio with a steered portion. In the steering control device according to claim 3,
When performing the fixed gear ratio steer-by-wire control, the steering control means increases the torque output from the steering reaction force actuator as the cable extension amount decreases, or increases the control followability of the steering actuator. A steering control device that performs at least one of the two operations. In the steering control device according to claim 4,
Actuator use frequency equivalent value detecting means for detecting a use frequency equivalent value of the steering reaction force actuator and the steering actuator is provided,
When the steering control means executes the fixed gear ratio steer-by-wire control, the smaller the cable extension amount, the larger the torque output from the steering reaction force actuator and the control followability of the steering actuator, In addition, the steering control device determines the loads of both actuators so that the load is not biased to one of the actuators according to the actuator use frequency equivalent value. The steering control device according to any one of claims 3 to 5,
A cable tension estimating means for estimating the tension of the backup cable is provided,
The steering control means performs the steer-by-wire control during the fixed gear ratio steer-by-wire control when the estimated cable tension is equal to or greater than a predetermined value, and performs angular position deviation due to a difference between the steering angle and the turning angle. After the correction, the steering control device again performs the fixed gear ratio steer-by-wire control by mechanically connecting the steering unit and the steered unit again by the backup cable. The steering control device according to any one of claims 3 to 6,
A cable tension estimating means for estimating the tension of the backup cable is provided,
The steering control means, when executing the fixed gear ratio steer-by-wire control, reduces the control followability of the steered actuator if the estimated cable tension is equal to or greater than a predetermined value, or a command used for steer control. A steering control device that performs at least one of three operations: a value of a turning angle is made smaller than usual or a torque output from the steering reaction force actuator is made larger than usual. The steering control device according to any one of claims 1 to 7,
Provide a notification means for notifying the driver of the abnormality of the steering control system,
The steering control device is characterized in that when the cable abnormality determining means determines that the cable is abnormal, the notification means notifies the abnormality. A steering part having a steering wheel and a steering reaction force actuator, and a steering part having a steering wheel and a steering actuator can be mechanically separated and connected via a backup cable.
Steer-by-wire control is performed by turning the steering unit and the steered unit, and turning the steering control to make a turning angle according to the steering state, and the steering reaction force control giving the steering reaction force according to the turning state. In the steering control device for performing the steering assist control by connecting the steering unit and the steered unit via the backup cable and performing at least one of the steering reaction force actuator and the steered actuator as an assisting means,
When it is determined that the steer-by-wire control is possible, the steering assist control is not executed even if it is determined that the cable is abnormal because the cable extension amount is equal to or greater than a predetermined value. .

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