JP2007308098A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and certainly make a steering wheel and a reference point of a turned wheel coincident and to sense sufficient reaction force by a driver. <P>SOLUTION: ECU 45 for check determines whether or not a detection steering angle θ satisfies a first linear advancement determination condition at step S34 and determines whether or not a steering angle θ satisfies a second linear advancement determination condition at step S35. If the first condition is only satisfied, ECU 45 connects/controls an electromagnetic clutch 22 for connecting a mechanical reaction force giving mechanism 23 and a steering input shaft 12 at step S37. Further, the present detection steering angle θ and the detecting turning angle δ are updated to temporary steering 0 point θkc_0 and temporary turning 0 point δkc_0 at step S39. Further, if a second condition is satisfied, ECU 45 connects/controls the clutch 22 at step S40 again and updates the present detection steering angle θ and the detection turning angle δ to the final steering 0 point θc_0 and the turning 0 point δc_0 at step S42. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a steering device for a steering-by-wire vehicle.

Conventionally, the steering wheel and the steered wheel are mechanically separated, and the steered wheel is steered by operating the steered actuator provided on the steered wheel side according to the steering operation of the steering handle. 2. Description of the Related Art A vehicle steering apparatus that employs a steering-by-wire system in which a reaction force actuator provided on a steering handle side according to an operation is controlled to apply a steering reaction force is well known. In this type of vehicle steering device, for example, as shown in Patent Document 1 below, the steering wheel as a steering handle responds to a steering operation even when the steering motor as a steering actuator is abnormal. In order to ensure the turning of the steered wheels, a connecting / disconnecting means (electromagnetic clutch) is disposed between the steering wheel and the steered wheels, and normally the connecting / disconnecting means is set in a disconnected state, and the steering wheel and the steered wheels are set. When the steering motor is abnormal, the connecting / disconnecting means is set in a connected state so that the steering wheel and the steered wheel are coupled. In this conventional vehicle steering apparatus, the steered wheels are steered to a position corresponding to the steering position of the steering wheel by the steered motor prior to the coupling by the connecting / disconnecting means.
JP 2001-260908 A

  Incidentally, in general, in the case of a steering device for a steering-by-wire vehicle, for example, a large amount of turning is performed with a small amount of operation so that a predetermined relationship is established between the amount of operation of the steering wheel and the amount of turning of the steered wheels. The steered wheels are steered so that the steer amount is obtained. In other words, the steering wheel side and the steered wheel side operate independently. For this reason, even if the steered wheel is corrected and steered before the connecting / disconnecting means connects the steering wheel and the steered wheel from such an independent operation state, the steering position on the steered wheel side and the steered position on the steered wheel side It is extremely difficult to make these completely match. That is, in a situation where the steering wheel side and the steered wheel side operate independently, the steering handle steering reference point and the steered wheel steering reference point may not match, and thus It becomes extremely difficult to completely match the steering position of the steering wheel with the steered wheel steered position based on different reference points.

  In addition, in this type of vehicle steering device, in addition to applying a reaction force by operating a reaction force actuator in response to an operation of a steering handle by a driver, for example, it is generated by an elastic member such as a spring. It is also done to give a resilient reaction force. In this case, for example, in a state where the steering reference point (for example, neutral position) of the steering wheel and the steering reference point (for example, neutral position) of the steered wheel do not match, the steering handle and the steered wheel are mechanically When coupled, the reaction force applied by the reaction force actuator can be adjusted as appropriate, but the reaction force applied from the elastic member cannot be adjusted. For this reason, the driver may perceive an unintended reaction force in the vicinity of the neutral position of the steering wheel, for example, and may feel uncomfortable.

  The present invention has been made to solve the above-described problems, and the object thereof is to make it possible to easily and accurately match the steering reference point of the steering wheel and the steering reference point of the steered wheel. An object of the present invention is to provide a steering-by-wire vehicle steering apparatus that allows a driver to perceive a favorable reaction force in the vicinity of a position.

  In order to achieve the above object, the present invention is characterized by a steering handle that is steered by a driver to turn a vehicle, a reaction force actuator that applies a reaction force to the operation of the steering handle, and a steered wheel A steering actuator for turning the steering wheel, and in response to an operation of the steering handle, the reaction force actuator is driven and controlled to apply a predetermined reaction force, and the steering actuator is driven and controlled to control the turning wheel. In a steering-by-wire vehicle steering apparatus provided with a steering control device, the control device includes an operation input value detection means for detecting an operation input value of a driver for the steering handle, and steering of the steered wheels. A steering amount detecting means for detecting the amount and an operation input value detected by the operation input value detecting means are set in advance to determine a straight traveling state of the vehicle. Based on the determination by the determination unit that determines whether or not the straight-running determination condition is satisfied, and the determination unit that the detected operation input value satisfies the straight-running determination condition of the vehicle. The steering reference point of the steering handle is updated using the detected operation input value, and the turning amount detected by the turning amount detection means corresponding to the detected operation input value that satisfies the straight-running determination condition of the vehicle is determined. And a reference point updating means for updating the steering reference point of the steered wheels. In this case, the steering wheel and the steered wheel are interposed between the steered wheel and the steered wheel, disconnecting the steered handle and the steered wheel in a non-coupled state so that power cannot be transmitted, and in the coupled state, the steering handle and the steered wheel. It is preferable to provide a backup interrupter that connects the steering wheel so that power can be transmitted.

  According to this, the control device satisfies the vehicle straight-running determination condition for determining the straight-running state of the vehicle by the determining unit using the operation input value (for example, the steering angle) detected by the operation input value detecting unit. It can be determined whether or not. Then, if the vehicle is in a straight traveling state based on the determination by the determination unit, the control device detects the operation input currently detected as the steering reference point (for example, the neutral position of the steering wheel) by the reference point update unit. It can be updated to a value and updated to a steered amount (for example, steered angle) currently detected as a steered wheel reference point (for example, neutral position of steered wheels). Accordingly, the control device constantly obtains (learns) an accurate reference point by repeatedly updating the steering reference point and the turning reference point using the operation input value and the turning amount detected by the reference point updating means. )be able to. Therefore, for example, even when an abnormality occurs in the operation of the steering device of the vehicle and the backup interrupter mechanically connects the steering handle and the steered wheel, based on the updated steering reference point and steered reference point. The operation input value and the steered amount can be detected accurately, and the steering position of the steering wheel and the steered position of the steered wheels can be accurately matched and connected.

  Further, in this case, the straight traveling determination condition of the vehicle is that the operation input value detected by the operation input value detection means is continued for a predetermined first time in a state where the operation input value is smaller than the first operation input value. And the predetermined input in a state where the operation input value detected by the operation input value detecting means is smaller than the second operation input value set smaller than the first operation input value. And a second straight-running determination condition for determining that the second time set longer than the first time is continued, and the reference point update means is configured to detect the operation input detected. Based on the determination by the determination means that the value satisfies only the first straight travel determination condition, the steering handle steering reference point is provisionally set using the detected operation input value that satisfies the first straight travel determination condition. And update In addition, the turning reference point is provisionally updated using the turning amount detected by the turning amount detection means corresponding to the detected operation input value that satisfies the first straight traveling determination condition, and the detection Based on the determination by the determination means that the operation input value that has been satisfied satisfies the second straight travel determination condition, the steering handle steering reference point is finally determined using the detected operation input value that satisfies the second straight travel determination condition. And the steering reference point is finally updated using the turning amount detected by the turning amount detection means corresponding to the detected operation input value that satisfies the second straight traveling determination condition. Good. In this case, the control device further includes vehicle speed detection means for detecting a vehicle speed, and the determination means has the detected operation input value when the detected vehicle speed is smaller than a predetermined vehicle speed set in advance, It may be determined whether or not the first straight traveling determination condition or the second straight traveling determination condition is satisfied.

  According to these, the reference point update means can tentatively update the steering reference point and the turning reference point when the detected operation input value satisfies the first straight traveling determination condition, and is detected. When the operation input value satisfies the second straight traveling determination condition, the steering reference point and the turning reference point can be updated finally. Here, the second straight traveling determination condition is a condition for determining the straight traveling state of the vehicle more strictly than the first straight traveling determination condition. For this reason, when the detected operation input value satisfies the first straight-running determination condition, the reference point update unit first provisionally sets the steering reference point and the turning reference point with a certain error range. Update it. Then, the reference point update means finally updates the steering reference point and the turning reference point within a very small error range when the detected operation input value satisfies the second straight traveling determination condition. In this way, by increasing the opportunity to update (learn) the steering reference point and the steering reference point, the control device can set an accurate reference point extremely easily and reliably. Further, by executing such reference point update, that is, learning of the reference point, in a low speed region, the influence on the steering operation by the driver can be reduced.

  Another feature of the present invention is that a mechanical reaction force applying mechanism that applies a mechanically resilient reaction force to the operation of the steering handle, and between the steering handle and the mechanical reaction force applying mechanism are provided. The steering handle and the mechanical reaction force applying mechanism are connected in a connected state so as to be able to transmit power, and the steering handle and the mechanical reaction force applying mechanism are disabled in a disconnected state. A switch for switching the interrupter from a disconnected state to a connected state based on a determination by the determination means that the detected operation input value satisfies a straight traveling condition of the vehicle. There is also a configuration including a control means.

  According to this, in addition to (or instead of) the reaction force actuator, in addition to the reaction force actuator, even when the mechanical reaction force application mechanism applies a mechanically resilient reaction force to the vehicle steering device, in particular, the steering In the vicinity of the steering reference point (for example, neutral position) of the steering wheel, the driver can perceive an appropriate reaction force characteristic. That is, when the straight traveling state of the vehicle is determined by the determination unit of the control device, the switching control unit switches the interrupter from the unconnected state to the connected state (when already in the connected state, it is temporarily switched from the unconnected state to the connected state). By switching, the steering reference point of the steering wheel and the reaction force application reference point of the mechanical reaction force application mechanism (for example, the neutral position where the reaction force is “0”) can be matched. Thereby, a resilient reaction force can be appropriately applied to the operation of the steering wheel based on the reaction force characteristic of the mechanical reaction force application mechanism set in advance. Therefore, the driver does not feel uncomfortable with the reaction force perceived through the steering wheel.

  Another feature of the present invention is that the control means sets a large reaction force to be applied by the reaction force actuator until the reference point update means updates the steering reference point and the turning reference point. is there. In this case, the control means has a characteristic of a reaction force applied by the reaction force actuator, and a viscosity component characteristic that changes according to the operation speed of the steering handle is greatly increased with respect to a change in the operation speed of the steering handle. The reaction force applied by the reaction force actuator may be set large by changing the characteristics to change.

  According to this, until the reference point update unit updates the steering reference point and the steering reference point, the control unit sets a large reaction force to be applied to the operation of the steering wheel, and uses the set reaction force. It is applied to the reaction force actuator. At this time, the control means changes the viscosity component characteristic among the reaction force characteristics of the reaction force actuator to set a large reaction force. Thereby, for example, when updating the neutral position of the steering wheel as the steering reference point, a greater reaction force is applied to the driver's operation of the steering wheel in the vicinity of the neutral position, more specifically to the operation speed of the steering wheel. can do. Accordingly, the steering wheel can be appropriately guided to the vicinity of the neutral position, and as a result, the straight-running determination condition of the vehicle can be easily satisfied, and the steering reference point and the turning reference point can be updated (learned) at an early stage. .

  Furthermore, another feature of the present invention is that the control means detects the turning amount of the steered wheels that has a predetermined exponential relationship or a power relationship with the operation input value detected by the operation input value detection means. Steering amount calculation means for calculating using the operation input value, and steering control means for controlling the turning actuator according to the calculated turning amount and turning the steered wheels to the same calculated turning amount. It also has a configuration with.

  According to this, the steered wheels can be steered to the steered amount calculated using the detected operation input value in a state where the steering reference point and the steered reference point coincide with each other. As a result, the steered wheels can be steered accurately according to the operation of the steering handle by the driver. Therefore, the vehicle can be turned appropriately, and the driver can obtain a good steering feeling.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a vehicle steering apparatus according to this embodiment. The vehicle steering device includes a steering operation device 10 that is steered by a driver, a mechanical reaction force device 20 that applies a mechanically resilient reaction force to the driver's steering operation, and a steered wheel. And a steering device 30 that steers the left and right front wheels FW1 and FW2 in accordance with the steering operation of the driver, and adopts a steering-by-wire system in which the steering operation device 10 and the steering device 30 can be mechanically separated. Yes.

  The steering operation device 10 includes a steering handle 11 that is rotated by a driver. The steering handle 11 is fixed to the upper end of the steering input shaft 12, and a steering reaction force electric motor (reaction force actuator) 13 is assembled to an intermediate portion of the input shaft 12. The steering reaction force electric motor 13 drives the steering input shaft 12 to rotate about the axis via the speed reduction mechanism 14. Further, a mechanical reaction force device 20 is assembled to the steering input shaft 12 so that a mechanical reaction force can be transmitted.

  The mechanical reaction device 20 includes a rotation transmission mechanism 21 that transmits the rotation of the steering input shaft 12. The rotation transmission mechanism 21 includes a predetermined gear mechanism and a shaft, and transmits the rotation of the steering input shaft 12 to the mechanical reaction force applying mechanism 23 via an electromagnetic clutch 22 as an interrupter. The electromagnetic clutch 22 is set in a connected state in an energized state and is set in a non-connected state in a non-energized state. The electromagnetic clutch 22 transmits the rotation from the rotation transmission mechanism 21 to the mechanical reaction force applying mechanism 23 in the connected state, and does not transmit the rotation from the rotation transmission mechanism 21 to the mechanical reaction force applying mechanism 23 in the non-connected state.

  The mechanical reaction force applying mechanism 23 applies a mechanical reaction force to the turning operation of the steering handle 11, that is, the steering input shaft 12, when the electromagnetic clutch 22 is in the connected state. The mechanical reaction force applying mechanism 23 includes a rotating shaft 23 a connected to the electromagnetic clutch 22. The mechanical reaction force applying mechanism 23 is provided in a non-rotatable manner in the casing 23b, and is attached to a screw portion formed on the rotating shaft 23a, and a nut 23c that moves forward and backward in the axial direction by the rotation of the rotating shaft 23a. I have. A hook-shaped spring pressing piece 23d is integrally formed on the outer periphery of the nut 23c. Between the spring pressing piece 23d and the spring receivers 23e and 23f provided on the upper and lower surfaces of the casing 23a, respectively. An upper coil spring 23g1 and a lower coil spring 23g2 are provided. In the following description, the upper coil spring 23g1 and the lower coil spring 23g2 are collectively referred to simply as a spring 23g. Further, the upper coil spring 23g1 and the lower coil spring 23g2 may be configured by appropriately combining a plurality of coil springs according to the change characteristics of the reaction force to be applied.

  In the mechanical reaction force application mechanism 23 configured as described above, a mechanical reaction force is applied to the turning operation of the steering handle 11 by the driver as described below. That is, when the electromagnetic clutch 22 is in the connected state, the rotation of the steering input shaft 12 accompanying the turning operation of the steering handle 11 is transmitted to the rotating shaft 23 a via the rotation transmitting mechanism 21 and the electromagnetic clutch 22. Thereby, when the rotating shaft 23a rotates, the nut 23c assembled to the screw portion formed on the coaxial 23a moves upward or downward against the elastic force of the spring 23g.

  More specifically, when the driver rotates the steering handle 11 in the right direction, for example, the nut 23c moves upward to compress the upper coil spring 23g1. When the driver rotates the steering handle 11 in the left direction, for example, the nut 23c moves downward to compress the lower coil spring 23g2. As described above, the elastic restoring force resulting from the compression of the upper coil spring 23g1 or the lower coil spring 23g2 is transmitted to the steering handle 11 via the rotating shaft 23a, the electromagnetic clutch 22, the rotation transmitting mechanism 21, and the steering input shaft 12, and the driver. Is perceived as a mechanical reaction force. Note that the reaction force applied by the mechanical reaction force applying mechanism 23 is “0” in a neutral position described later, and changes to a large value as the absolute value of the rotation operation amount of the steering handle 11 increases.

  The steering device 30 includes a rack bar 31 that extends in the left-right direction of the vehicle. Left and right front wheels FW1, FW2 are connected to both ends of the rack bar 31 via a tie rod and a knuckle arm (not shown) so as to be steerable. The left and right front wheels FW1, FW2 are steered left and right by the axial displacement of the rack bar 31. On the outer periphery of the rack bar 31, a steering electric motor (steering actuator) 32 assembled in a housing (not shown) is provided. The rotation of the steering electric motor 32 is decelerated by the screw feed mechanism 33 and is converted into an axial displacement of the rack bar 31. Further, the steering device 30 includes a steering output shaft 34 that can rotate about an axis. A pinion gear 35 is fixed to the lower end of the steered output shaft 34, and the pinion gear 35 meshes with rack teeth 31 a provided on the rack bar 31, and the rack bar is rotated by rotation around the axis of the steered output shaft 34. 31 is displaced in the axial direction.

  Further, a backup electromagnetic clutch 36 as a backup interrupter is provided at the upper end of the steering output shaft 34. The backup electromagnetic clutch 36 is set to a non-connected state in the energized state, and is set to a connected state in the non-energized state, and integral rotation of the steering input shaft 12 and the steering output shaft 34 is prohibited by the non-connected state. Then, the integrated rotation of the steering input shaft 12 and the steered output shaft 34 is allowed depending on the connected state.

  Next, the electric control device 40 that controls the operation of the steering reaction force electric motor 13, the electromagnetic clutch 21, the steering electric motor 32, and the backup electromagnetic clutch 36 will be described. The electric control device 40 includes a steering angle sensor 41, a steering torque sensor 42, a turning angle sensor 43, and a vehicle speed sensor 44.

  The steering angle sensor 41 is assembled to the steering input shaft 12, and detects the steering zero point as the steering reference point of the steering handle 11 (steering input shaft 12), that is, the rotation angle from the neutral position, and serves as the steering angle θ. Output. The steering torque sensor 42 is also assembled with the steering input shaft 12 and outputs the torque input to the steering handle 11 by the driver as the steering torque T. The turning angle sensor 43 is assembled to the rack bar 31 and detects the amount of axial displacement of the rack bar 31 from the turning zero point as a turning reference point, that is, the neutral position, and the left and right front wheels FW1, FW2 (turning It outputs as the actual turning angle δ of the rudder output shaft 34). The vehicle speed sensor 44 detects and outputs the vehicle speed V. Here, each of these sensors 41 to 44 continuously outputs detection values at a predetermined extremely short cycle.

  In the present specification, the above-described steering zero point and steering zero point (that is, neutral position) are the steering handle 11, the steering input shaft 12, and the mechanical reaction force applying mechanism 23 for maintaining the vehicle in a straight traveling state. It refers to the position of the rotary shaft 23a, the steering output shaft 34, and the left and right front wheels FW1, FW2. The steering angle θ and the actual turning angle δ are output as “0” at the neutral position, and the right rotation angle is expressed as a positive value and the left rotation angle is expressed as a negative value. Further, the steering torque T represents a torque applied in the right direction as a positive value and a torque applied in the left direction as a negative value.

  The electric control device 40 includes a check electronic control unit (hereinafter referred to as a check ECU) 45, a steering reaction force electronic control unit (hereinafter referred to as a steering reaction force ECU) 46, and a steering electronic control unit (hereinafter referred to as a steering reaction force ECU). 47) (referred to as steering ECU). A steering angle sensor 41, a steering torque sensor 42, a turning angle sensor 43, and a vehicle speed sensor 44 are connected to the check ECU 45. A steering angle sensor 41, a steering torque sensor 42, and a vehicle speed sensor 44 are connected to the steering reaction force ECU 46. A steering angle sensor 41, a steering angle sensor 43, and a vehicle speed sensor 44 are connected to the steering ECU 47.

  Each of these ECUs 45 to 47 has a microcomputer including a CPU, a nonvolatile memory (for example, EEPROM), a volatile memory (for example, a RAM), a timer and the like as main components, and is connected to be communicable with each other. Has been. The check ECU 45 performs switching control of the connected state or the disconnected state of the electromagnetic clutch 22 via the drive circuit 51 and executes the “initial operation check program” in FIG. 2 and the “0 point learning program” in FIG. . The steering reaction force ECU 46 executes the “steering reaction force control program” of FIG. 5, and drives and controls the steering reaction force electric motor 13 via the drive circuit 52. The steering ECU 47 executes the “steering control program” in FIG. 6, and drives and controls the steering electric motor 32 via the drive circuit 53.

  Further, the steering ECU 47 switches the connection state or the non-connection state of the abnormality electromagnetic clutch 36 via the drive circuit 54 depending on whether or not an abnormality has occurred in the operation of the steering electric motor 32. To do. Note that whether or not an abnormality has occurred in the operation of the steering electric motor 32 is, for example, when the difference value between the steering angle θ and the actual turning angle δ is greater than a predetermined value or the actual turning angle. This is determined based on a case where the change speed of δ (that is, the turning angular speed dδ / dt) is less than a predetermined turning angular speed.

  Next, the operation of the embodiment configured as described above will be described. When an ignition switch (not shown) is turned on by the driver, the checking ECU 45 executes the “initial operation check program” only once after the ignition switch is turned on, and starts executing the “0-point learning program”. . Here, the “initial operation check program” is executed only once during the turning operation of the steering wheel 11 by the first driver after the ignition switch is turned on, for example.

  In addition, when the ignition switch is turned on, the steering reaction force ECU 46 and the turning ECU 47 start to repeatedly execute the “steering reaction force control program” and the “steering control program”, respectively, every predetermined short time. When the ignition switch is turned on, the steering ECU 47 energizes the backup electromagnetic clutch 36 in cooperation with the drive circuit 53 to control the electromagnetic clutch 36 in a non-connected state. .

  The execution of the “initial operation check program” is started in step S10 of FIG. 2 after execution of an initialization process (not shown), and the check ECU 45 cooperates with the drive circuit 51 in step S11. Is energized to control the electromagnetic clutch 22 to a connected state. Then, the check ECU 45 inputs the steering torque T detected by the steering torque sensor 42 in the subsequent step S12, and proceeds to step S13. In step S13, the check ECU 45 determines whether or not the electromagnetic clutch 22 is normally connected based on the magnitude of the input steering torque T. Hereinafter, this determination will be specifically described.

  When the electromagnetic clutch 22 is normally connected according to the processing of step S11, the rotation of the steering input shaft 12 that rotates integrally with the steering handle 11 is transmitted via the rotation transmission mechanism 21 and the electromagnetic clutch 22. And transmitted to the mechanical reaction force applying mechanism 23. Thereby, in the mechanical reaction force applying mechanism 23, as described above, the nut 23c compresses the spring 23g with the rotation of the rotating shaft 23a, and an elastic restoring force resulting from this compression is generated. Therefore, if the electromagnetic clutch 22 is in the connected state, the steering handle 11 is turned, whereby the reaction force caused by the elastic restoring force (hereinafter, the reaction force caused by the elastic restoring force is referred to as a spring reaction force Ts). ) Is given. In other words, the driver rotates the steering handle 11 by inputting the predetermined steering torque T while perceiving the applied spring reaction force Ts.

  This will be described in more detail with reference to FIG. FIG. 3 schematically shows a change characteristic of the steering torque T with respect to the steering angle θ. When the electromagnetic clutch 22 is in a non-connected state, for example, accompanying the turning operation of the steering handle 11, that is, the turning of the steering input shaft 12, accompanying the rotation of the electric motor 13 for frictional force, inertial force, and steering reaction force, for example. Viscous forces and the like are generated, and these forces are input to the steering input shaft 12. For this reason, as shown by a solid line in FIG. 3, the driver inputs a predetermined torque Tg substantially equal to the reaction force perceived as the steering handle 11 is turned. On the other hand, since the spring reaction force Ts is applied when the electromagnetic clutch 22 is in the connected state, the driver perceives a reaction force larger than the predetermined torque Tg. For this reason, as shown by a broken line in FIG. 3, the driver inputs a steering torque T larger than a predetermined torque Tg to the steering handle 11 to perform a turning operation.

  Therefore, when the electromagnetic clutch 22 is normally connected, the steering torque T having a change characteristic as indicated by a broken line in FIG. Thereby, if the steering torque T detected by the steering torque sensor 42 is larger than the predetermined torque Tg by the spring reaction force Ts, the check ECU 45 is operating normally. In step S13, it determines with "Yes" and progresses to step S14. On the other hand, if the steering torque T detected by the steering torque sensor 42 is equal to or less than the predetermined torque Tg, the check ECU 45 maintains the non-coupled state against the coupling control. If “No” is determined, the process proceeds to step S17. In step S17, an abnormality flag MBF indicating the normal operation state or abnormal operation state of the electromagnetic clutch 22 is set to "1" indicating the abnormal operation state of the electromagnetic clutch 22, and in step S18, an "initial operation check program" The execution of is terminated.

  In step S <b> 14, the check ECU 45 cuts off the energization of the electromagnetic clutch 22 in cooperation with the drive circuit 51, and controls the electromagnetic clutch 22 to be in a disconnected state. In step S15, the check ECU 45 determines whether the steering torque T detected by the steering torque sensor 42 is equal to or less than a predetermined torque Tg. That is, as described above, if the electromagnetic clutch 22 is normally disconnected, the steering torque T detected by the steering torque sensor 42 is equal to or less than the predetermined torque Tg, and therefore the check ECU 45 determines “Yes”. And the process proceeds to step S16. In step S <b> 16, the check ECU 45 sets the abnormality flag MBF to “0” indicating the normal operation state of the electromagnetic clutch 22. In step S18, the execution of the “initial operation check program” is terminated.

  On the other hand, when the electromagnetic clutch 22 maintains the connected state against the non-connected control, the steering torque T detected by the steering torque sensor 42 is larger than the predetermined torque Tg as described above. Therefore, if the detected steering torque T is greater than the predetermined torque Tg, the check ECU 45 determines “No” and proceeds to step S17, sets the abnormality flag MBF to “1”, and in step S18. The execution of the “initial operation check program” is terminated.

  Further, after the ignition switch is turned on, the check ECU 45 repeatedly executes the “0-point learning program” in FIG. 4 every predetermined short time following the execution of the “initial operation check program” described above. This “0-point learning program” is the zero point, that is, the neutral position of each of the steering input shaft 12 (steering handle 11), the rotational shaft 23a of the mechanical reaction force applying mechanism 23, and the turning output shaft 34 (left and right front wheels FW1, FW2). Are corrected so that they match. Here, the checking ECU 45 executes the “0-point learning program” while continuously acquiring each detection value output from the steering angle sensor 41, the turning angle sensor 43, and the vehicle speed sensor 44 at a predetermined extremely short cycle. It shall be. In addition, when the “0-point learning program” is executed for the first time in the current travel, the steering 0 point and the steering 0 point (that is, the neutral position) stored in the nonvolatile memory (EEPROM) at the end of the previous travel are used as a reference. It is assumed that the detected steering angle θ and turning angle δ from the steering angle sensor 41 and the turning angle sensor 43 are adopted.

  The execution of the “0-point learning program” is started in step S30 after execution of an initialization process (not shown), and the check ECU 45 determines whether or not the abnormality flag MBF is set to “0” in step S31. Confirm. That is, if the abnormality flag MBF is set to “1” by executing the “initial operation check program” described above, the checking ECU 45 determines “No” and proceeds to step S33, and the “0-point learning program”. The execution of is terminated. Then, the checking ECU 45 notifies the driver that an abnormality has occurred in the operation of the electromagnetic clutch 22, for example, by causing an alarm to generate an alarm according to an abnormality processing program (not shown). In this case, although there is a possibility that good reaction force characteristics as will be described later may not be obtained, the vehicle can be driven safely.

  On the other hand, if the abnormality flag MBF is set to “0” by executing the “initial operation check program” described above, the checking ECU 45 determines “Yes” in step S31 and proceeds to step S32. In step S32, after the ignition switch is turned on, the check ECU 45 sets a learning completion flag FRG_A indicating that learning of 0 points has been completed to “0” indicating that learning has not yet been completed. It is determined whether or not it has been done. That is, if the learning completion flag FRG_A is set to “0”, it is necessary to learn 0 points, so the checking ECU 45 determines “Yes” and proceeds to step S34. On the other hand, if the learning completion flag FRG_A is set to “1” indicating that learning of 0 points has already been completed, the checking ECU 45 ends the execution of the “0 point learning program” in step S33.

  In step S34, the check ECU 45 determines whether or not the vehicle satisfies the first straight traveling determination condition. Here, the first straight-running determination condition is that the vehicle speed V continuously input from the vehicle speed sensor 44 at a very short cycle is smaller than the preset vehicle speed V0 and is continuously from the steering angle sensor 41 at a very short cycle. The condition where the absolute value | θ | of the steering angle θ that is inputted is smaller than the preset steering angle θ0 continues for the time t0. The vehicle speed V0, the steering angle θ0, and the duration time t0 in the first straight travel determination condition are set to values that are somewhat large. For this reason, the first straight travel determination condition has a certain amount of error, that is, is set as a rough straight travel determination condition.

  In step S34, the check ECU 45 starts a timer for measuring the duration time t0, determines whether or not the traveling state of the vehicle satisfies the first straight traveling determination condition, If the straight traveling determination condition is satisfied, “Yes” is determined, and the process proceeds to step S35. On the other hand, if the first straight-running determination condition is not satisfied, the vehicle is not currently in the straight-running state, so it is determined as “No”, the process proceeds to step S46, the timer is cleared, and “0-point learning is performed in step S47. Execution of “program” is temporarily terminated. Then, after a predetermined short time has elapsed, the “0-point learning program” is executed again, and the execution of the program is repeated until the learning completion flag FRG_A is set to “1”.

  In step S35, the check ECU 45 determines whether or not the vehicle satisfies the second straight traveling determination condition. Here, the second straight traveling determination condition is that the vehicle speed V continuously input from the vehicle speed sensor 44 at a very short cycle is smaller than the preset vehicle speed V1 and is continuously from the steering angle sensor 41 at a very short cycle. In other words, the condition that the absolute value | θ | of the steering angle θ that is input is smaller than the preset steering angle θ1 continues for the time t1. The vehicle speed V1 and the steering angle θ1 in the second straight travel determination condition are set to values smaller than the vehicle speed V0 and the steering angle θ0 in the first straight travel determination condition. Further, the duration t1 is set to a value larger than the duration t0 in the first straight traveling determination condition. For this reason, the second straight travel determination condition is set as a more strict straight travel determination condition.

  In step S35, the check ECU 45 starts a timer for measuring the duration time t1, and determines whether or not the traveling state of the vehicle satisfies the second straight traveling determination condition. If the second straight-running determination condition is not satisfied in step S35, the checking ECU 45 determines “No” and performs each process of step S36 to step S39 (hereinafter, step S36 to step S39). The processes are collectively called a provisional 0-point learning process). On the other hand, if the second straight-running determination condition is satisfied in step S35, the checking ECU 45 determines “Yes” and performs each processing of step S40 to step S45 (hereinafter, step S40 to step S45). Each process is collectively called a final 0-point learning process). Hereinafter, the provisional 0-point learning process and the final 0-point learning process will be specifically described.

  The provisional 0-point learning process is “Yes” in Step S34 and “No” in Step S35, that is, the first straight-running determination condition is satisfied, but the second straight-running determination condition is It is executed when it does not satisfy. In other words, the steering handle 11 (steering input shaft 12), the rotating shaft 23a of the mechanical reaction force applying mechanism 23, and the left and right front wheels FW1, FW2 (steering output shaft 34) in a situation where the first straight traveling determination condition is satisfied. Each of the 0 points, that is, the neutral position is tentatively learned. Therefore, each 0 point learned by the provisional 0-point learning process is a rough 0 point having a certain amount of error. Specifically, the provisional 0-point learning process is described. The check ECU 45 clears the measurement of the duration t1 in step S36 based on the “No” determination in step S35.

  Subsequently, in step S37, the check ECU 45 controls the connection of the electromagnetic clutch 22. That is, the check ECU 45 energizes the electromagnetic clutch 22 with a predetermined drive current in cooperation with the drive circuit 51 to bring the electromagnetic clutch 22 into a connected state. When the provisional learning process is executed again, the checking ECU 45 once controls the electromagnetic clutch 22 to be disconnected and then performs connection control. In this case, since the “initial operation check program” is executed and it is confirmed that the electromagnetic clutch 22 operates normally, the electromagnetic clutch 22 is normally engaged. After the connection control process in step S37, the check ECU 45 makes a “No” determination in step S38 until the time tr required for the operation to ensure that the electromagnetic clutch 22 is in the connected state has elapsed from the start of the connection control. Repeatedly, when the time tr elapses, it is determined as “Yes”, and the process proceeds to Step S39.

  In step S39, the checking ECU 45 sets the steering angle θ input at the time when “Yes” is determined in step S34 to θkc_0 representing the provisional steering zero point. Further, the check ECU 45 sets the turning angle δ input from the turning angle sensor 43 at the time point determined as “Yes” in the step S34 to δkc_0 representing the provisional 0 turning point. After the setting process in step S39, the checking ECU 45 proceeds to step S47, and temporarily ends the execution of the “0 point learning program”. Then, after a predetermined short time has elapsed, the “0-point learning program” is executed again, and the execution of the program is repeated until the learning completion flag FRG_A is set to “1”.

  Here, as described above, when the provisional 0-point learning process is executed, the steering handle 11 (steering input shaft 12), the rotating shaft 23a of the mechanical reaction force applying mechanism 23, and the left and right front wheels FW1, FW2 (steering output shaft) Each zero point of 34) or the neutral position can be matched within a certain small range. As a result, the driver can drive the vehicle straight by maintaining the steering handle 11 in the substantially neutral position, and the mechanical reaction force applying mechanism at the substantially neutral position based on the characteristics of the spring reaction force Ts described later. The spring reaction force Ts imparted by 23 is not perceived. When the driver rotates the steering handle 11, the steering reaction force ECU 46 and the steering ECU 47, as described later, are based on the temporary steering 0 point and the temporary steering 0 point. Perform reaction force control and steering control. Therefore, it becomes difficult for the driver to feel uncomfortable with respect to the change characteristic of the steering reaction force applied with the turning operation of the steering handle 11, and the vehicle can be turned appropriately.

  Next, the final 0-point learning process will be described. The final 0-point learning process is executed when it is determined as “Yes” in both step S34 and step S35, that is, when a more strict second straight traveling determination condition is satisfied. Therefore, the final 0-point learning process is performed at 0 points, that is, neutral positions of the steering handle 11 (steering input shaft 12), the rotating shaft 23a of the mechanical reaction force applying mechanism 23, and the left and right front wheels FW1, FW2 (steering output shaft 34). Is determined more accurately.

  Specifically, the final 0-point learning process will be described. The check ECU 45 controls the operation of the electromagnetic clutch 22 in step S40 based on the “Yes” determination in step S35. That is, the check ECU 45 cooperates with the drive circuit 51 to control the electromagnetic clutch 22 that is currently in a connected state to a non-connected state by executing the provisional 0-point learning process described above. After a predetermined time th required for the operation to become, the control is again performed in the connected state. As described above, once the electromagnetic clutch 22 is controlled to be in the non-connected state, the temporary steering zero point of the steering input shaft 12 and the rotation of the mechanical reaction force applying mechanism 23 associated with each other by the provisional zero point learning process. The relationship with the zero point of the shaft 23a is released.

  Subsequently, in step S41, the check ECU 45 repeatedly executes “No” determination until the time tr required for the operation for ensuring that the electromagnetic clutch 22 is in the connected state has elapsed since the start of the connection control, and the time tr When elapses, “Yes” is determined, and the process proceeds to step S42. As a result, the steering zero point of the steering input shaft 12 that satisfies the second straight traveling determination condition coincides with the balance position of the spring 23g, that is, the zero point of the rotary shaft 23a by the non-connection control of the electromagnetic clutch 22 in the step S40. Associated with each other in the state.

  In step S42, the checking ECU 45 sets the steering angle θ input at the time when “Yes” is determined in step S35 to θc_0 representing the final steering zero point. Further, the checking ECU 45 sets the turning angle δ input from the turning angle sensor 43 at the time point determined as “Yes” in the step S35 to δc_0 representing the final zero turning point. Thus, by setting the steering 0 point θc_0 and the turning 0 point δc_0, the steering handle 11 (steering input shaft 12) that satisfies the second straight traveling determination condition, and the rotating shaft 23a of the mechanical reaction force applying mechanism 23. In addition, the right and left front wheels FW1 and FW2 (steering output shaft 34) are set in a state in which the accurate zero point, that is, the accurate neutral position is matched.

  Then, after the setting process of step S42, the check ECU 45 is in a state where the absolute value | θ | of the steering angle θ continuously detected at a predetermined extremely short cycle is smaller than the predetermined steering angle θ1 in step S43. It is determined whether or not the above is maintained. By executing the determination process in step S43, for example, it is possible to effectively prevent the final 0-point learning process from being executed while the driver is gently turning the steering handle 11. .

  That is, if the absolute value | θ | of the steering angle θ is greater than or equal to the predetermined steering angle θ1, in other words, if the second straight-running determination condition is not satisfied at the time of execution of step S43, the checking ECU 45 is “No”. The process proceeds to step S47, and the execution of the program is temporarily terminated. In this case, the final 0-point learning has not yet been completed, and the check ECU 45 starts executing the “0-point learning program” again after a predetermined short time has elapsed, and the learning completion flag FRG_A Repeat program execution until is set to "1".

  On the other hand, if the absolute value | θ | of the steering angle θ is smaller than the predetermined steering angle θ1, in other words, if the second straight-running determination condition is satisfied at the time of execution of step S43, the checking ECU 45 determines “Yes”. And the process proceeds to step S44. In step S44, the check ECU 45 sets the learning completion flag FRG_A to “1” indicating that the zero-point learning processing is completed, and steers the learning completion flag FRG_A set to “1” in step S45. This is output to the reaction force ECU 46 and the steering ECU 47. Then, the checking ECU 45 ends the execution of the “0 point learning program” in step S47.

  Further, the steering reaction force ECU 46 repeatedly executes the “steering reaction force control program” of FIG. 5 every predetermined short time after turning on the ignition switch. The execution of this “steering reaction force control program” is started in step S50, and the steering reaction force ECU 46 inputs the steering angle θ from the steering angle sensor 41 and the vehicle speed V from the vehicle speed sensor 44 in step S51. The process proceeds to step S52. In step S52, the steering reaction force ECU 46 determines whether or not the learning completion flag FRG_A set to “1” has been acquired from the check ECU 45.

  That is, if the steering reaction force ECU 46 has acquired the learning completion flag FRG_A set to “1”, as described above, the steering 0 point θc_0 of the steering handle 11 (steering input shaft 12) and the mechanical reaction force Since learning is completed in a state where the zero point of the rotating shaft 23a of the providing mechanism 23 is exactly matched, it is determined as “Yes”. Then, the steering reaction force ECU 46 executes each processing of step S53 to step S56, and applies an appropriate reaction force to the turning operation of the steering handle 11 by the driver. 13 is controlled (hereinafter, this drive control is referred to as normal reaction force control). Hereinafter, the normal reaction force control will be described in detail.

In step S53, the steering reaction force ECU 46 refers to the motor reaction force characteristic table stored in advance in the nonvolatile memory, and changes the steering reaction force electric motor 13 according to the steering angle θ and the vehicle speed V. The target reaction force by (hereinafter, this reaction force is referred to as target motor reaction force Tm ^* ) is calculated. As shown in FIG. 7, the motor reaction force characteristic table stores a plurality of target motor reaction forces Tm * that increase nonlinearly as the absolute value | θ | of the steering angle θ increases for each of a plurality of representative vehicle speed values. is doing. Instead of using the motor reaction force characteristic table, a target motor reaction force Tm * that changes according to the steering angle θ and the vehicle speed V is defined in advance by a function, and the target motor is used by using the function. The reaction force Tm * may be calculated.

  Next, in step S54, the steering reaction force ECU 46 refers to a spring reaction force characteristic table stored in advance in the nonvolatile memory, and calculates a spring reaction force Ts that changes according to the steering angle θ. . As shown in FIG. 8, this spring reaction force characteristic table is a characteristic that increases as the absolute value | θ | of the steering angle θ increases. In particular, the absolute value | θ | of the steering angle θ changes within a small range. The spring reaction force Ts that increases the rate is stored.

As described above, when the target motor reaction force Tm ^* and the spring reaction force Ts corresponding to the steering angle θ are calculated in step S53 and step S54, respectively, the steering reaction force ECU 46 performs target steering in step S55. Calculate reaction force Th ^* . Specifically, the target steering reaction force Th ^* is calculated by adding the target motor reaction force Tm ^* calculated in step S53 and the spring reaction force Ts calculated in step S54 according to the following equation 1. To do.
Th ^* = Tm ^* + Ts ... Formula 1

In this embodiment, the target motor reaction force Tm ^* and the spring reaction force Ts are calculated, and these reaction forces are added according to the above-described equation 1 to calculate the target steering reaction force Th ^* . However, for example, a steering reaction force table storing a plurality of target steering reaction forces Th * that change according to the steering angle θ and the vehicle speed V is prepared in advance in a nonvolatile memory, and the steering reaction force table is referred to. Then, the target steering reaction force Th ^* may be calculated. Further, instead of using this steering reaction force table, a target steering reaction force Th ^* that changes according to the steering angle θ and the vehicle speed V is defined in advance by a function, and the target steering reaction force is calculated by using the function. The force Th ^* may be calculated.

Next, in step S56, the steering reaction force ECU 46 corresponds to the calculated target steering reaction force Th ^* in cooperation with the drive circuit 52. More specifically, the steering reaction force ECU 46 corresponds to the target motor reaction force Tm ^*. An electric current is supplied to the steering reaction force electric motor 13 and the execution of the “steering reaction force control program” is temporarily ended in step S59. Thereby, the steering reaction force electric motor 13 drives the steering input shaft 12 with a rotational torque corresponding to the target motor reaction force Tm ^* . As a result, the target steering reaction force Th ^* by the steering reaction force electric motor 13 and the mechanical reaction force applying mechanism 23 is applied to the turning operation of the steering handle 11, and the driver feels an appropriate steering reaction force. However, the steering handle 11 can be turned. In this case, the normal reaction force control is performed when the learning completion flag FRG_A is set to “1”, that is, the steering 0 point of the steering handle 11 (steering input shaft 12) and the rotation shaft 23a of the mechanical reaction force applying mechanism 23. It is executed in a state where the zero point exactly matches. For this reason, an unnecessary reaction force at the zero point of the steering handle 11, that is, a neutral position, more specifically, an unnecessary spring reaction force Ts is not applied, and thus the driver obtains a good steering feeling. be able to.

  On the other hand, if the steering reaction force ECU 46 has acquired the learning completion flag FRG_A set to “0” from the checking ECU 45, the zero-point learning process has not been completed yet, and therefore, “No” in step S52. Is determined. Then, the steering reaction force ECU 46 executes steps S57 and S58, and in order to complete the final 0-point learning process in the execution of the above-described “0-point learning program” at an early stage, the steering handle 11 (the steering input shaft 12). In particular, the steering reaction force electric motor 13 is driven and controlled so that the motor reaction force in the vicinity of the temporary steering zero point is increased (hereinafter, this increased motor reaction force is referred to as a motor reaction force Tml) ( Hereinafter, this drive control is referred to as learning assist reaction force control). Hereinafter, this learning assistance reaction force control will be described in detail.

  In step S57, the steering reaction force ECU 46 refers to the viscosity component characteristic table of the steering reaction force electric motor 13 stored in advance in the nonvolatile memory, and changes with time of the steering angle θ, that is, the steering angular velocity dθ / dt. The viscosity component Tmr is changed so as to increase. As shown in FIG. 9, the viscous component characteristic table includes a steering angular velocity for each set value of the learning completion flag FRG_A, that is, “1” indicating after completion of 0-point learning or “0” indicating completion of 0-point learning. A viscosity component Tmr that linearly increases as the absolute value | dθ / dt | of dθ / dt increases is stored. Here, in FIG. 9, the viscosity component Tmr after completion of learning is indicated by a solid line, and the viscosity component Tmr before completion of learning is indicated by a broken line. Instead of using this viscosity component characteristic table, the viscosity component Tmr that changes in accordance with the set value of the learning completion flag FRG_A and the absolute value | dθ / dt | of the steering angular velocity dθ / dt is defined in advance by a function. The viscosity component Tmr corresponding to the set value of the learning completion flag FRG_A may be calculated using the same function.

Next, in step S58, the steering reaction force ECU 46 calculates the target motor reaction force Tml ^* reflecting the viscosity component Tmr changed so as to increase in step S57, and also calculates the calculated target motor reaction force. A force Tml ^* is applied to the steering handle 11. More specifically, the steering reaction force ECU 46 calculates the target motor reaction force Tml ^* using the motor reaction force characteristic table shown in FIG. Here, the calculated target motor reaction force Tml ^* reflects the viscosity component Tmr changed so as to increase as described above. Therefore, the calculated target motor reaction force Tml ^* depends on the magnitude of the viscosity component Tmr, that is, the magnitude of the steering angular velocity dθ / dt of the steering wheel 11 by the driver. Therefore, the target motor reaction force Tml ^* calculated in the learning assist reaction force control is the target motor in the normal reaction force control, as shown by the broken line in FIG. 7, in accordance with the turning operation of the steering handle 11 by the driver. Larger than the reaction force Tm. Needless to say, the target motor reaction force Tml ^* is changed according to whether the electromagnetic clutch 22 is connected or not, that is, depending on the presence or absence of the spring reaction force Ts.

The steering reaction force ECU 46 cooperates with the drive circuit 52 to flow a drive current corresponding to the calculated target motor reaction force Tml ^* to the steering reaction force electric motor 13, and this “steering” in step S 59. The execution of the “reaction force control program” is once terminated. Thereby, the steering reaction force electric motor 13 drives the steering input shaft 12 with a rotational torque corresponding to the target motor reaction force Tml ^* . As a result, it is possible to apply a larger reaction force to a fast turning operation of the steering handle 11 by the driver, and particularly to a turning operation in the vicinity of the temporary steering 0 point, that is, in the vicinity of the neutral position. It becomes easy to guide the steering handle 11 in the direction of the temporary steering zero point by the large reaction force. Accordingly, when the “0-point learning program” is executed by the check ECU 45, the second straight-running determination condition in step S36 is easily established, and the final 0-point learning process is easily completed early.

  Further, after turning on the ignition switch, the steering ECU 47 repeatedly executes the “steering control program” of FIG. 6 every predetermined short time. Execution of the “steering control program” is started in step S70, and the steering ECU 47 determines that the steering angle sensor 41 determines the steering angle θ and the steering angle sensor 43 determines the actual steering angle δ and the steering angle sensor 43 in step S71. The vehicle speed V is input from the vehicle speed sensor 44, and the process proceeds to step S72.

In step S72, the turning ECU 47 refers to the turning angle table stored in the non-volatile memory, and calculates the target turning angle δ ^* that changes according to the steering angle θ. As shown in FIG. 10, the turning angle table stores a target turning angle δ ^* that increases nonlinearly as the absolute value | θ | of the steering angle θ increases. The rate of change of the target turning angle δ ^* with respect to the steering angle θ is set to be small within a small range of the absolute value | θ | of the steering angle θ and to increase as the absolute value | θ | of the steering angle θ increases. ing. Instead of using the turning angle table, a function (for example, an exponential function or a power function) indicating the relationship between the steering angle θ and the target turning angle δ ^* is prepared in advance. May be used to calculate the target turning angle δ ^* . The target turning angle δ ^* may be calculated using, for example, the lateral acceleration and yaw rate that are generated when the vehicle turns, or the turning curvature of the vehicle.

  Next, in step S73, the steering ECU 47 refers to the vehicle speed coefficient table stored in the non-volatile memory, and calculates the vehicle speed coefficient K that changes according to the vehicle speed V. As shown in FIG. 11, the vehicle speed coefficient table is larger than “1” within a small range of the vehicle speed V, smaller than “1” within a large range of the vehicle speed V, and becomes “1” as the vehicle speed V increases. The vehicle speed coefficient K that decreases nonlinearly is stored. Instead of using this vehicle speed coefficient table, a function indicating the relationship between the vehicle speed V and the vehicle speed coefficient K is prepared in advance, and the vehicle speed coefficient K may be calculated using the function. .

After determining the target turning angle δ ^* and the vehicle speed coefficient K, the steering ECU 47 corrects the target turning angle δ ^* by the vehicle speed coefficient K in step S74 by executing the calculation of the following equation (2). The final target turning angle δ ^* is calculated.
δ ^* = K · δ ^* … Formula 2

  Next, the steering ECU 47 determines whether or not the learning completion flag FRG_A set to “1” has been acquired from the check ECU 45. That is, if the steering ECU 47 has acquired the learning completion flag FRG_A set to “1”, as described above, the final steering 0 point θc_0 of the steering handle 11 (steering input shaft 12) and the left and right Since learning is completed in a state where the final turning 0 point δc_0 of the front wheels FW1, FW2 (steering output shaft 34) exactly matches, it is determined as “Yes”.

Then, in step S76, the turning ECU 47 sets the turning 0 point δc_0 to the neutral position, and turns the turning angle δ ^* so that the actual turning angle δ finally becomes equal to the target turning angle δ ^{* .} , Δ difference δ ^* −δ is used to control the rotation of the steering electric motor 32 via the drive circuit 54. As a result, the steering electric motor 32 is rotationally driven and drives the rack bar 31 in the axial direction via the screw feed mechanism 33 to steer the left and right front wheels FW1, FW2 to the target turning angle δ ^* . Then, in step S78, the steering ECU 47 once terminates the execution of the steering control program, and starts executing the program again after a predetermined short period of time.

On the other hand, if the turning ECU 47 has acquired the learning completion flag FRG_A set to “0” from the checking ECU 45, the final 0-point learning process has not yet been completed. Is determined. As a result, the turning ECU 47 sets the temporary turning 0 point δkc_0 to the neutral position in step S77, and the actual turning angle δ is finally equal to the target turning angle δ ^* as in step S76. Thus, the rotation of the steering electric motor 32 is controlled via the drive circuit 54 using the difference δ ^* −δ between the turning angles δ ^* and δ. Then, in step S78, the steering ECU 47 once terminates the execution of the steering control program, and starts executing the program again after a predetermined short period of time.

  As described above, as shown in FIG. 10, the left and right front wheels FW1 and FW2 are steered small with respect to the change in the steering angle θ within a small range of the steering angle θ by the steering control in step S76 or step S77. The steering is greatly steered with respect to the change of the steering angle θ within a large range of the steering angle θ. As a result, the left and right front wheels FW1, FW2 are steered to a large turning angle δ without changing the steering handle 11. As shown in FIG. 11, the left and right front wheels FW1, FW2 are steered greatly with respect to the steering angle θ when the vehicle speed V is low, and are steered small with respect to the steering angle θ when the vehicle speed V increases. As a result, the driver can obtain a good steering feeling according to the vehicle speed V.

  As can be understood from the above description, according to the present embodiment, when the detected steering angle θ satisfies the first straight-running determination condition, the checking ECU 45 temporarily provisional steering 0 point θkc_0. In addition, the temporary turning 0 point δkc_0 can be updated. When the detected steering angle θ satisfies the second straight traveling determination condition, the accurate steering 0 point θc_0 and the accurate turning 0 point δc_0 can be updated finally.

  Here, the second straight traveling determination condition is a condition for determining the straight traveling state of the vehicle more strictly than the first straight traveling determination condition. Therefore, when the detected steering angle θ satisfies the first straight traveling determination condition, the check ECU 45 firstly has a temporary steering 0 point θkc_0 and a temporary turning 0 point having a certain error range. Δkc_0 can be provisionally updated. Then, when the detected steering angle θ satisfies the second straight traveling determination condition, the check ECU 45 finally determines the accurate steering 0 point θc_0 and the accurate steering 0 point δc_0 within an extremely small error range. Can be updated. Thus, by increasing the opportunity to update (learn) the steering 0 point and the turning 0 point, the steering 0 point θc_0 and the turning 0 point δc_0 as the accurate reference points are set extremely easily and reliably. be able to. Further, by performing such updating of the steering 0 point and the steering 0 point in a low speed region where the detected vehicle speed V is low, the influence on the steering operation by the driver can be reduced.

  Further, in addition to (or instead of) the steering reaction force electric motor 13, in particular, even when the mechanical reaction force applying mechanism 23 applies a mechanically resilient spring reaction force Ts, the steering handle 11 in particular. In the vicinity of the steering 0 point θc_0 (that is, the neutral position) of the (steering input shaft 12), the driver can perceive an appropriate reaction force characteristic. That is, when the check ECU 45 determines the straight traveling state of the vehicle based on the second straight traveling determination condition, the check ECU 45 controls the electromagnetic clutch 22 to the re-coupled state, thereby controlling the steering 0 point of the steering handle 11 (the steering input shaft 12). θc_0 and the zero point of the mechanical reaction force applying mechanism 23 can be matched. Thereby, a resilient spring reaction force Ts can be appropriately applied to the operation of the steering handle 11 based on the reaction force characteristic of the mechanical reaction force applying mechanism 23 set in advance. Therefore, the driver does not feel uncomfortable with the reaction force perceived via the steering wheel 11.

Further, until the steering 0 point θc_0 and the turning 0 point δc_0 are finally updated, the steering reaction force ECU 46 changes the viscosity component characteristic of the reaction force characteristic of the steering reaction force electric motor 13. The steering reaction force electric motor 13 performs drive control so as to apply a large target motor reaction force Tml ^* to the steering handle 11. Thereby, for example, a greater reaction force can be applied to the operation of the steering handle 11 by the driver in the vicinity of the neutral position of the steering handle 11, more specifically to the operation speed of the steering handle 11. Accordingly, the steering handle 11 can be appropriately guided to the vicinity of the neutral position, and as a result, the second straight traveling determination condition is easily satisfied, and the checking ECU 45 sets the steering 0 point θc_0 and the turning 0 point δc_0. It can be updated (learned) early.

  By the way, by executing the zero point learning program in the above embodiment, the steering handle 11 (steering input shaft 12), the rotating shaft 23a of the mechanical reaction force applying mechanism 23, and the left and right front wheels FW1, FW2 (steering output shaft 34). Each zero point, that is, the neutral position can be surely matched. Therefore, for example, even when an abnormality occurs in the steering state of the left and right front wheels FW1 and FW2, the steering handle 11 (steering input shaft 12), the rotating shaft 23a of the mechanical reaction force applying mechanism 23, and the left and right front wheels FW1, With the neutral position of FW2 (steering output shaft 34) matched, the steering ECU 47 can control the abnormality electromagnetic clutch 36 to the connected state very easily. Thus, even when the steering handle 11 and the left and right front wheels FW1, FW2 are mechanically connected when an abnormality occurs, the driver can make the vehicle travel straight or turn extremely easily, Good reaction force characteristics can be obtained.

  Furthermore, in carrying out the present invention, the present invention is not limited to the above-described embodiments and modifications, and various modifications can be made without departing from the object of the present invention.

  For example, in the above-described embodiment, the execution of the program is terminated after the processing of Step S40 to Step S45 in the “0 point learning program”, that is, the final 0 point learning processing. However, it is possible to repeatedly execute the “0 point learning program” as necessary.

  In the above embodiment, the steering handle 11 that is turned to steer the vehicle is used. However, instead of this, for example, a joystick-type steering handle that is linearly displaced may be used, or any other one that can be operated by the driver and instructed to steer the vehicle is used. May be.

  In the above embodiment, the steering electric motor 32 linearly displaces the rack bar 31 to steer the left and right front wheels FW1, FW2. Instead, the left and right front wheels FW1 and FW2 may be steered by the turning electric motor 32 rotating the turning output shaft 34.

1 is an overall schematic diagram of a vehicle steering apparatus according to an embodiment of the present invention. 2 is a flowchart of an initial operation check program executed by the check ECU in FIG. 1. It is a graph which shows the relationship between a steering angle and steering torque, Comprising: It is a figure for demonstrating the change of the steering torque at the time of the connection of an electromagnetic clutch, or a non-connection. It is a flowchart of the 0 point learning program performed by ECU for a check of FIG. It is a flowchart of the steering reaction force control program executed by the steering reaction force ECU of FIG. It is a flowchart of the steering control program performed by ECU for steering of FIG. It is a graph which shows the relationship between a steering angle and a target motor reaction force. It is a graph which shows the relationship between a steering angle and a spring reaction force. It is a graph which shows the viscosity component characteristic of the electric motor for steering reaction forces of FIG. It is a graph which shows the relationship between a steering angle and a target turning angle. It is a graph which shows the relationship between a vehicle speed and a vehicle speed coefficient.

Explanation of symbols

FW1, FW2 ... front wheels, 11 ... steering handle, 12 ... steering input shaft, 13 ... electric motor for steering reaction force, 21 ... rotation transmission mechanism, 22 ... electromagnetic clutch, 23 ... mechanical reaction force applying mechanism, 31 ... rack bar, 32 ... Electric motor for turning, 34 ... Steering output shaft, 41 ... Steering angle sensor, 42 ... Steering torque sensor, 43 ... Steering angle sensor, 44 ... Vehicle speed sensor, 45 ... ECU for check, 46 ... Steering reaction force ECU, 47 ... ECU for turning

Claims (8)

A steering handle that is steered by a driver to turn the vehicle, a reaction force actuator that applies a reaction force to the operation of the steering handle, a turning actuator for turning steered wheels, and the steering handle A steering-by-wire vehicle including a control device that drives and controls the reaction force actuator to apply a predetermined reaction force and steers the steered wheel by driving the steering actuator according to the operation of In the steering apparatus, the control device is
An operation input value detecting means for detecting an operation input value of a driver for the steering wheel;
A turning amount detecting means for detecting a turning amount of the turning wheel;
A determination unit that determines whether or not the operation input value detected by the operation input value detection unit satisfies a vehicle straight-running determination condition that is set in advance in order to determine the vehicle straight-running state;
Based on the determination by the determining means that the detected operation input value satisfies the straight-ahead determination condition of the vehicle, the steering reference point of the steering wheel is determined using the detected operation input value that satisfies the straight-line determination condition of the vehicle. A reference point update that updates and updates the turning reference point of the steered wheels by using the turning amount detected by the turning amount detection means corresponding to the detected operation input value that satisfies the straight-running determination condition of the vehicle And a vehicle steering apparatus. In the vehicle steering apparatus according to claim 1,
The straight traveling determination condition for the vehicle is as follows:
A first straight-running determination condition for determining that the operation input value detected by the operation input value detection means is continued for a predetermined first time in a state where the operation input value is smaller than the first operation input value;
A second value set longer than the predetermined first time in a state where the operation input value detected by the operation input value detection means is smaller than the second operation input value set smaller than the first operation input value; And a second straight-running determination condition for determining that the time is continued,
The reference point update means includes
Based on the determination by the determination means that the detected operation input value satisfies only the first straight travel determination condition, the steering handle steering reference is determined using the detected operation input value that satisfies the first straight travel determination condition. The turning reference point is provisionally updated using the turning amount detected by the turning amount detection means corresponding to the detected operation input value that satisfies the first straight traveling determination condition. Update
Based on the determination by the determining means that the detected operation input value satisfies the second straight travel determination condition, the steering handle steering reference point is determined using the detected operation input value that satisfies the second straight travel determination condition. Is finally updated, and the turning reference point is finally determined using the turning amount detected by the turning amount detection means corresponding to the detected operation input value that satisfies the second straight traveling determination condition. A vehicle steering apparatus that is updated to The vehicle steering apparatus according to claim 2, further comprising:
Vehicle speed detection means for detecting the vehicle speed,
The determination means includes
When the detected vehicle speed is smaller than a predetermined vehicle speed set in advance, it is determined whether or not the detected operation input value satisfies the first straight travel determination condition or the second straight travel determination condition. A vehicle steering apparatus. The vehicle steering apparatus according to claim 1, further comprising:
A mechanical reaction force applying mechanism that mechanically applies a reaction force to the operation of the steering handle; and a steering reaction state between the steering handle and the mechanical reaction force applying mechanism. An interrupter that connects the steering handle and the mechanical reaction force application mechanism so as to be able to transmit power, and disconnects the steering handle and the mechanical reaction force application mechanism in a non-coupled state so as not to transmit power;
The control device;
A vehicle comprising switching control means for switching the interrupter from a non-connected state to a connected state based on the determination by the determining means that the detected operation input value satisfies a straight traveling condition of the vehicle. Steering device. In the vehicle steering apparatus according to claim 1,
The control means includes
The vehicle steering apparatus according to claim 1, wherein the reaction force applied by the reaction force actuator is set large until the reference point update unit updates the steering reference point and the steering reference point. In the vehicle steering apparatus according to claim 5,
The control means includes
By changing the characteristic of the reaction force applied by the reaction force actuator, which changes depending on the operation speed of the steering wheel, to a characteristic that greatly changes with the change in the operation speed of the steering wheel. A vehicle steering apparatus characterized in that a reaction force applied by the reaction force actuator is set large. In the vehicle steering apparatus according to claim 1,
The control means;
Steering amount calculation means for calculating the turning amount of the steered wheels that is in a predetermined exponential relationship or a power relationship with the operation input value detected by the operation input value detection means, using the detected operation input value;
A vehicle steering apparatus comprising: a steering control unit that controls the steering actuator according to the calculated turning amount to turn the turning wheel to the calculated turning amount. . The vehicle steering apparatus according to claim 1, further comprising:
It is interposed between the steering handle and the steered wheel, disconnects the steering handle and the steered wheel in a non-connected state so that power cannot be transmitted, and connects the steered handle and the steered wheel in a connected state. A vehicle steering apparatus comprising a backup interrupter connected to transmit power.

Images