Steering control device and steering control method

Abstract

To provide a steering control device and a steering control method capable of detecting a mechanical abnormality of a turning unit in the steer-by-wire type steering device.SOLUTION: A steering control device is applied to a vehicular steering system that includes a steer-by-wire type steering device. The steering control device executes an activation-time process and a turning unit abnormality determining process. The activation-time process is a process for enabling a steering control on the running of a vehicle after the vehicular steering system is turned on. The turning unit abnormality determining process is a process for determining the presence or absence of a mechanical abnormality in the turning unit while the activation-time process is being executed after the vehicular steering system is turned on. The steering control on the running of the vehicle is configured to be not executable when it is determined that there is a mechanical abnormality in the turning unit, and to be executable when it is determined that there is no mechanical abnormality in the turning unit.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a steering control device and a steering control method. [Background technology]

[0002] Conventionally, steering devices mounted on vehicles include a steering force assist device that uses a motor as a drive source to apply an assist force to a steering system to assist steering operation. For example, as described in Patent Document 1, a steering control device that controls such a steering device is capable of detecting mechanical abnormalities in the steering device and warning the driver.

[0003] In the above-mentioned Patent Document 1, an abnormality in the rack shaft is detected as a mechanical abnormality in the steering device using the detection result of a torque sensor provided in the steering device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-128943 Summary of the Invention [Problem to be solved by the invention]

[0005] Detecting an abnormality in the rack shaft is particularly important in so-called steer-by-wire steering systems in which the power transmission paths between the steering wheel and the steered wheels of the vehicle are separated, because even if an abnormality occurs in the rack shaft, the condition is not communicated to the driver through the steering wheel. [Means for solving the problem]

[0006] A steering control device that can solve the above problems is applied to a vehicle steering system that steers the running of a vehicle. The vehicle steering system comprises a steer-by-wire steering device having a structure in which power transmission paths are separated between a steering unit steered by a steering member of the vehicle and a steering unit that operates to steer the steered wheels of the vehicle, and the steering control device is configured to execute a startup process and a steering unit abnormality determination process, the startup process being a process for enabling control of steering the vehicle's traveling after the vehicle steering system is powered on, and the steering unit abnormality determination process being a process for determining whether or not there is a mechanical abnormality in the steering unit while controlling the operation of the steering unit after the vehicle steering system is powered on during execution of the startup process, and the control of steering the vehicle's traveling is configured to not be executed if it is determined in the steering unit abnormality determination process that there is a mechanical abnormality in the steering unit, and to be executed if it is determined in the steering unit abnormality determination process that there is no mechanical abnormality in the steering unit.

[0007] According to the above configuration, the steering unit abnormality determination process is executed while the vehicle steering system is powered on and control of steering the vehicle is not possible, i.e., while the startup process is being executed. During the startup process, the vehicle is in a state where it cannot run because control of steering the vehicle is not possible. In a situation where the vehicle cannot run, even if the steering unit is operated to determine whether or not there is an abnormality, the occurrence of an event such as the vehicle running in an unintended direction is suppressed. This ensures the safety of the driver even if the steering unit is operated to determine whether or not there is an abnormality. Therefore, a mechanical abnormality in the steering unit can be detected in a steer-by-wire steering device.

[0008] In the above steering control device, it is preferable that the startup processing includes processing for controlling the operation of the steering unit, and the steering unit abnormality determination processing is processing executed while the operation of the steering unit is being controlled in the startup processing.

[0009] According to the above configuration, while the startup process is being executed, the steering member is operated to make the driver aware that the vehicle is in a standby state before driving. While the driver is being made aware that the vehicle is in a standby state before driving, it is possible to make it difficult for the driver to realize that the steered wheels have been turned through the steering unit abnormality determination process. Therefore, it is possible to make it difficult for the driver to feel uncomfortable when the steering unit abnormality determination process is executed.

[0010] For example, the startup processing can be embodied to include processing for controlling the operation of the steering unit so as to rotate the steering wheel, which is the steering member, to a limit position in a first direction or a second direction, respectively.

[0011] Also, for example, the startup processing can be embodied to include processing for controlling the operation of the steering unit so as to align the rotational position of the steering wheel, which is the steering member, with the steering position of the steered wheels obtained through the steering unit.

[0012] In the above steering control device, the processing related to the control of steering the vehicle's travel includes a process of calculating a steering signal indicating the state of the steering unit, and a process of controlling the state of the steering unit so that the state corresponds to the steering signal, and the process of calculating the steering signal is a process that is executed even during the startup process after the vehicle steering system is powered on, and the process of controlling the state of the steering unit includes a dead zone setting process that sets a dead zone so that the state of the steering unit is not controlled in response to the steering signal during the startup process after the vehicle steering system is powered on, and it is preferable that the dead zone setting process includes a process of temporarily reducing the dead zone while the steering unit abnormality determination process is being executed.

[0013] According to the above configuration, the processing related to the control of steering the vehicle can be used for the steering unit abnormality determination processing, which makes it possible to keep the scale of design changes small even when the steering unit abnormality determination processing is executed.

[0014] For example, the dead zone setting process is a guard process that sets the dead zone by limiting the value of the control quantity for controlling the state of the steering unit in response to the steering signal to a guard value, and temporarily reducing the dead zone can be implemented to relax the restriction imposed by the guard value.

[0015] According to the above configuration, even when the steering unit abnormality determination process is executed, design changes can be easily made, which is effective in keeping the scale of design changes small. A steering control method that can solve the above problem is applied to a vehicle steering system that steers the traveling of a vehicle equipped with a steer-by-wire steering device having a structure in which a power transmission path between a steering unit steered by a steering member of the vehicle and a steering unit that operates to steer the steered wheels of the vehicle is separated. The steering control method includes executing a startup process and a steering unit abnormality determination process, the startup process being executed to enable control of steering the traveling of the vehicle after the vehicle steering system is powered on, the steering unit abnormality determination process being executed during execution of the startup process after the vehicle steering system is powered on to determine whether or not there is a mechanical abnormality in the steering unit while controlling the operation of the steering unit, and the control of steering the traveling of the vehicle is not enabled when it is determined in the steering unit abnormality determination process that there is a mechanical abnormality in the steering unit, and is enabled when it is determined in the steering unit abnormality determination process that there is no mechanical abnormality in the steering unit. [Effects of the Invention]

[0016] According to the present invention, a mechanical abnormality in a steering unit can be detected in a steer-by-wire steering device. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram showing the configuration of a steer-by-wire steering device according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the steering control device of FIG. 1. [Figure 3] 10 is a flowchart showing the procedure of a startup process executed by the steering CPU of FIG. 1 when the steering CPU is in a startup state. [Figure 4] 4 is a flowchart showing the procedure of the reaction force side normal control preparation process of FIG. 3. [Figure 5] 10 is a flowchart showing the procedure of a learning process. [Figure 6]4 is a flowchart showing the procedure of a normal control preparation process on the steering side in FIG. 3. [Figure 7] 5 is a flowchart showing the procedure of a steering unit abnormality determination process in the first embodiment. [Figure 8] 5A and 5B are diagrams illustrating the timing at which the steering unit abnormality determination process is executed in the first embodiment. [Figure 9] 10 is a flowchart showing the procedure of a steering unit abnormality determination process in the second embodiment. [Figure 10] 10(a) and 10(b) are diagrams illustrating the timing at which the steering unit abnormality determination process is executed in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] First Embodiment A steering control device according to a first embodiment will be described. As shown in FIG. 1, vehicle steering system 2 includes a steering control device 1. Vehicle steering system 2 includes a steering unit 4 and a steering unit 6. Steering unit 4 is steered by a driver via a steering wheel 3 of the vehicle, which is a steering member. Steering unit 6 steers left and right steered wheels 5 of the vehicle in accordance with the steering input to steering unit 4 by the driver. Vehicle steering system 2 has a structure in which, for example, the power transmission paths between steering unit 4 and steering unit 6 are always separated. The power transmission paths between steering actuator 12, which will be described later, and steering actuator 31, which will be described later, are always separated. In other words, vehicle steering system 2 includes a steer-by-wire type steering device.

[0019] The steering unit 4 includes a steering shaft 11 and a steering actuator 12. The steering shaft 11 is connected to the steering wheel 3. An end 11a of the steering shaft 11 opposite to the end connected to the steering wheel 3 has a stopper mechanism 11b. The stopper mechanism 11b defines the rotation range of the steering shaft 11. As a result, the rotation range of the steering wheel 3, which rotates integrally with the steering shaft 11, is defined by the stopper mechanism 11b. For example, the steering wheel 3 is rotatable within a rotation range between a right limit position 3a and a left limit position 3b.

[0020] The steering actuator 12 has a reaction motor 13 and a steering-side reduction gear mechanism 14. The reaction motor 13 is a steering-side motor that applies a steering reaction force, which is a force that resists steering, to the steering wheel 3 via the steering shaft 11. The reaction motor 13 is connected to the steering shaft 11 via the steering-side reduction gear mechanism 14, which is made up of, for example, a worm and wheel. The reaction motor 13 is, for example, a three-phase brushless motor.

[0021] The steering unit 6 includes a pinion shaft 21, a rack shaft 22 as a steering shaft, and a rack housing 23. The pinion shaft 21 and the rack shaft 22 are connected with each other at a predetermined cross angle. A rack-and-pinion mechanism 24 is formed by meshing pinion teeth 21a formed on the pinion shaft 21 with rack teeth 22a formed on the rack shaft 22. The pinion shaft 21 corresponds to a rotation axis that can be converted into a steering angle θi, which is the steering position of the steered wheels 5. The rack housing 23 accommodates the rack-and-pinion mechanism 24.

[0022] One end of the pinion shaft 21 opposite to the end connected to the rack shaft 22 protrudes from a rack housing 23. Both ends of the rack shaft 22 protrude from both axial ends of the rack housing 23. Tie rods 26 are connected to both ends of the rack shaft 22 via rack ends 25 made up of ball joints. The ends of the tie rods 26 are connected to knuckles (not shown) to which the left and right steered wheels 5 are respectively attached.

[0023] The steering unit 6 includes a steering actuator 31. The steering actuator 31 includes a steering motor 32, a transmission mechanism 33, and a conversion mechanism 34. The steering motor 32 is a steering-side motor that applies a steering force to the rack shaft 22 to turn the steerable wheels 5 via the transmission mechanism 33 and the conversion mechanism 34. The steering motor 32 transmits rotation to the conversion mechanism 34 via the transmission mechanism 33, which is, for example, a belt transmission mechanism. The transmission mechanism 33 converts the rotation of the steering motor 32 into reciprocating motion of the rack shaft 22 via the conversion mechanism 34, which is, for example, a ball screw mechanism. The steering motor 32 may be, for example, a three-phase brushless motor.

[0024] In vehicle steering system 2, steering actuator 31 applies motor torque as a steering force to rack shaft 22 in response to steering by the driver, thereby changing the steering angle θi of steered wheels 5. At this time, steering actuator 12 applies a steering reaction force that resists the steering by the driver to steering wheel 3. As a result, in vehicle steering system 2, the steering reaction force, which is the motor torque applied from steering actuator 12, changes the steering torque Th required to steer steering wheel 3.

[0025] The reason for providing the pinion shaft 21 is to support the rack shaft 22 together with the pinion shaft 21 inside the rack housing 23. The rack shaft 22 is supported movably along its axial direction and is pressed toward the pinion shaft 21 by a support mechanism (not shown) provided in the vehicle steering system 2. In this way, the rack shaft 22 is supported inside the rack housing 23. However, another support mechanism may be provided to support the rack shaft 22 in the rack housing 23 without using the pinion shaft 21.

[0026] <Electrical configuration of the steering system> 1, the reaction force motor 13 and the steering motor 32 are connected to the steering control device 1. The steering control device 1 controls the operation of each of the motors 13, 32.

[0027] Detection results of various sensors are input to the steering control device 1. The various sensors include, for example, a torque sensor 41, a steering side rotation angle sensor 42, a turning side rotation angle sensor 43, a vehicle speed sensor 44, and a pinion absolute angle sensor 45.

[0028] Torque sensor 41 is provided on steering shaft 11 between steering wheel 3 and steering-side reduction mechanism 14. Torque sensor 41 detects steering torque Th, which is a value indicating the torque applied to steering shaft 11 by the driver's steering. Steering torque Th is detected in relation to the torsion of a torsion bar 41a provided on steering shaft 11 between steering wheel 3 and steering-side reduction mechanism 14, midway along steering shaft 11. Steering-side rotation angle sensor 42 is provided on reaction motor 13. Steering-side rotation angle sensor 42 detects rotation angle θa, which is the rotation angle of the rotation shaft of reaction motor 13, within a range of 360 degrees. Turning-side rotation angle sensor 43 is provided on steering motor 32. Steering-side rotation angle sensor 43 detects rotation angle θb, which is the rotation angle of the rotation shaft of steering motor 32, within a range of 360 degrees. Vehicle speed sensor 44 detects vehicle speed V, which is the traveling speed of the vehicle. The pinion absolute angle sensor 45 is provided on the pinion shaft 21. The pinion absolute angle sensor 45 detects the pinion absolute rotation angle θabp, which is the actual measurement value of the angle of the rotation axis of the pinion shaft 21, in a range exceeding 360°.

[0029] A power supply system 46 is connected to the steering control device 1. The power supply system 46 has a battery 47. The battery 47 is a secondary battery mounted on the vehicle, and serves as the power source for supplying power to operate the reaction force motor 13 and the steering motor 32. The battery 47 also serves as the power source for supplying power to operate the steering control device 1.

[0030] A vehicle start switch 48 ("SW" in FIG. 1), such as an ignition switch, is provided between the steering control device 1 and the battery 47. The start switch 48 is provided midway on the power feeder L2, which branches off from the power feeder L1, one of two power feeders L1 and L2 connecting the steering control device 1 and the battery 47. The start switch 48 is operated when activating various functions to activate a driving source for running the vehicle, such as an engine, to enable operation of the vehicle. The conduction of the power feeder L2 is turned on and off through operation of the start switch 48. The operating state of the vehicle steering system 2 is associated with the operating state of the vehicle. Note that the power feeder L1 is basically always on, but the conduction of the power feeder L1 is indirectly turned on and off as a function of the vehicle steering system 2 depending on the operating state of the vehicle steering system 2. The operating state of the vehicle steering system 2 is associated with the on and off of the conduction of the power feeders L1 and L2, which is the state of the power supply from the battery 47. The operating state of the vehicle steering system 2 is powered on when the conduction of the power feeders L1, L2 is turned on based on the operation of the start switch 48. The operating state of the vehicle steering system 2 is powered off when the conduction of the power feeders L1, L2 is turned off based on the operation of the start switch 48.

[0031] <Functions of the steering control device> As shown in FIG. 2, steering control device 1 has reaction force control unit 50 and turning control unit 60. Reaction force control unit 50 controls steering wheel 3, which is the object to be controlled. Reaction force control unit 50 controls the drive of steering actuator 12, more specifically reaction force motor 13, in order to control the steering reaction force, which is the control variable of the object to be controlled. Turning control unit 60 controls rack shaft 22, which is the object to be controlled. Steering control unit 60 controls the drive of steering actuator 31, more specifically steering motor 32, in order to control the steering force, which is the control variable of the object to be controlled. Reaction force control unit 50 and turning control unit 60 transmit and receive information to and from each other via local network 49, for example, serial communication. Reaction force control unit 50 constitutes a reaction force system RS in combination with steering unit 4. Steering control unit 60 constitutes a steering system TS in combination with steering unit 6. The process by which reaction force control unit 50 controls the drive of reaction force motor 13 is called reaction force control processing. The process by which the steering control unit 60 controls the driving of the steering motor 32 is a steering control process.

[0032] The reaction force control unit 50 is equipped with a central processing unit (hereinafter referred to as "CPU") 50a and a memory 50b. The reaction force control unit 50 performs various processes by having the CPU 50a execute programs stored in the memory 50b at predetermined calculation cycles. The turning control unit 60 is equipped with a central processing unit (hereinafter referred to as "CPU") 60a and a memory 60b. The turning control unit 60 performs various processes by having the CPU 60a execute programs stored in the memory 60b at predetermined calculation cycles. The CPUs 50a, 60a and the memories 50b, 60b constitute a microcomputer, which is a processing circuit. The memories 50b, 60b include computer-readable media such as RAM (Random Access Memory) and ROM (Read Only Memory). However, it is an example that the various processes are realized by software. The processing circuits of the reaction force control unit 50 and the turning control unit 60 may be configured to realize at least a part of the processes by hardware circuits such as logic circuits.

[0033] CPU 50a in reaction force control unit 50 receives steering torque Th, vehicle speed V, rotation angle θa, and steering information St. Steering information St is obtained from steering control unit 60 via local network 49. Based on steering torque Th, vehicle speed V, rotation angle θa, and steering information St, CPU 50a calculates a control signal MSs to reaction force inverter 51 to control the steering reaction force. Reaction force inverter 51 is a drive circuit that converts the DC voltage of battery 47 into AC voltage and applies it to reaction force motor 13. In this process, CPU 50a references currents iu1, iv1, and iw1 flowing through reaction force motor 13. Currents iu1, iv1, and iw1 are quantified as voltage drops across shunt resistors provided in each leg of reaction force inverter 51. As a result, CPU 50a controls the drive of reaction force motor 13 to generate motor torque that serves as a steering reaction force.

[0034] The CPU 50a converts the rotation angle θa into an integrated rotation angle, i.e., an absolute rotation angle, which is an integrated value from the reaction force reference value θns stored in the memory 50b. The absolute rotation angle is a value converted within a range exceeding 360° by counting the number of rotations of the reaction force motor 13 from the reaction force reference value θns. The reaction force reference value θns is a value indicating, for example, a straight-ahead state, which is the steering state of the steering wheel 3 when the vehicle is traveling straight. The reaction force reference value θns is a value indicating a steering neutral position, which is the rotation position of the steering wheel 3 in the straight-ahead state, and is an example of control information. The CPU 50a calculates the steering angle θs by multiplying the absolute rotation angle obtained by the conversion by a conversion coefficient based on the rotational speed ratio of the steering-side reduction gear 14. The CPU 50a calculates the steering angle θs as an absolute angle relative to the steering neutral position, i.e., the reaction force reference value θns. The steering angle θs obtained in this manner is used to calculate the control signal MSs. Steering information Ss used by CPU 50 a, such as steering angle θs, is output to steering control section 60 via local network 49 .

[0035] CPU 60a in steering control unit 60 receives vehicle speed V, rotation angle θb, and steering information Ss. Steering information Ss is information obtained from reaction force control unit 50 via local network 49. Based on vehicle speed V, rotation angle θb, and steering information Ss, CPU 60a calculates a control signal MSt to be sent to steering inverter 61 to control the steering force. Steering inverter 61 is a drive circuit that converts the DC voltage of battery 47 into AC voltage and applies it to steering motor 32. In this process, CPU 60a references currents iu2, iv2, and iw2 that flow through steering motor 32. Currents iu2, iv2, and iw2 are quantified as the amount of voltage drop across shunt resistors provided in each leg of steering inverter 61. As a result, CPU 60a controls the drive of steering motor 32 so as to generate motor torque that serves as the steering force.

[0036] The CPU 60a converts the rotation angle θb into an integrated rotation angle, which is an integrated value from the steering reference value θnt stored in the memory 60b, i.e., an absolute rotation angle. The absolute rotation angle is a value converted within a range exceeding 360° by counting the number of rotations of the steering motor 32 from the steering reference value θnt. The steering reference value θnt is a value that indicates, for example, a straight-ahead state, which is the steering state of the rack shaft 22 when the vehicle is traveling straight. The steering reference value θnt is a value that indicates a rack neutral position, which is the position of the rack shaft 22 in the straight-ahead state, and is an example of control information. The CPU 60a calculates the pinion angle θp by multiplying the absolute rotation angle obtained by the conversion by a conversion coefficient based on the rotational speed ratio of the transmission mechanism 33, the lead of the conversion mechanism 34, and the rotational speed ratio of the rack and pinion mechanism 24. The CPU 60a calculates the pinion angle θp, which is the actual rotation angle of the pinion shaft 21, as an absolute angle relative to the rack neutral position, i.e., the steering reference value θnt. The pinion angle θp thus obtained is used to calculate the control signal MSt. The steering information St used by the CPU 60a, such as the pinion angle θp, is output to the reaction force control unit 50 via the local network 49.

[0037] <Processing to be performed during startup> When the power is off, after start switch 48 is turned on to turn on the power, CPU 50a transits through a start-up state to a normal control state. In this case, CPU 50a determines whether the power is on or off depending on whether or not the IG signal sg output by start switch 48 is input, and executes start-up processing including an initial check process and the like. Similarly, CPU 60a of steering control unit 60 determines whether the power is on or off, and executes start-up processing including an initial check process and the like. Hereinafter, when the CPU 50a of reaction force control unit 50 and the CPU 60a of steering control unit 60 are referred to collectively, they will be referred to as the "steering CPU."

[0038] As shown in Fig. 3, in the startup processing, the steering CPU executes an initial check processing (step 100). The initial check processing includes a check processing related to the operation of the reaction force system RS and the steering system TS, to check whether the CPUs and memories of the steering CPUs are operating normally. The initial check processing includes a check processing related to communication on the local network 49. The initial check processing includes a check processing related to reading out various information from memories corresponding to each of the steering CPUs. In the initial check processing, the various information read out by the steering CPUs from their corresponding memories includes the reaction force reference value θns and the steering reference value θnt.

[0039] For example, the initial check process executed by the CPU 60a includes a process of referencing the pinion absolute rotation angle θabp. The CPU 60a includes a process of calculating the number of rotations corresponding to the pinion absolute rotation angle θabp while referring to the pinion absolute rotation angle θabp. As a result, the CPU 60a includes a process of calculating a corrected pinion angle θpc obtained by correcting the rotation angle θb to an absolute rotation angle, which is an integrated rotation angle, based on the number of rotations. The CPU 60a also includes a process of writing and setting a steering midpoint value θct, which is a value corresponding to the rack neutral position for the corrected pinion angle θpc, into a steering reference value θnt.

[0040] Next, the steering CPU determines whether the normal control preparation process has been completed (step 102). In step 102, the steering CPU determines that the normal control preparation process has been completed if it can determine that the processes for the reaction force side and the steering side have been completed. The normal control preparation process will be described in detail later.

[0041] Next, when the steering CPU determines that the normal control preparation process has been completed (step 102: YES), it executes steering angle synchronization process (step 104). The steering angle synchronization process includes a process of synchronizing the relative positions of the steering wheel 3 and the steered wheels 5 by rotating the steering wheel 3. As a result of the steering angle synchronization process, the steering angle θs, which is the rotational position of the steering wheel 3, and the steering angle θi, which is the steered position of the steered wheels 5, i.e., the pinion angle θp, are synchronized so as to have a predetermined correspondence relationship.

[0042] The steering angle synchronization process is a process that is mainly executed by the CPU 50a, i.e., the reaction force side. For example, in step 104, the CPU 50a executes feedback processing to make the steering angle θs follow the steering target angle θs*. The steering target angle θs* is a value that corresponds to the pinion angle θp so that a predetermined correspondence is established. As a result, the CPU 50a calculates a control signal MSs for rotating the steering wheel 3 so that the steering angle θs and the pinion angle θp meet the predetermined correspondence. During the execution of the steering angle synchronization process, the CPU 50a outputs steering information Ss including the steering angle θs to the steering control unit 60 via the local network 49.

[0043] Thereafter, the steering CPU transitions to a normal control state, assuming that the startup processing is complete. The normal control state is a state in which control for steering the vehicle's traveling is executed, and in which normal reaction force processing and normal steering processing related to steering control for operating the steering unit 4 and the steering unit 6 in response to steering operations are executed. In this case, the reaction force system RS operates the steering unit 4 so as to operate in cooperation with the steering unit 6. Also, the steering system TS operates the steering unit 6 so as to operate in cooperation with the steering unit 4. For example, the normal steering processing executed by the CPU 60a includes processing for calculating a target pinion angle θp*, which is a target angle of the pinion angle θp corresponding to the steering angle θs, based on the steering angle θs included in the steering information Ss. The normal steering processing includes feedback processing for causing the pinion angle θp to follow the target pinion angle θp*. As a result, the CPU 60a calculates a control signal MSt for satisfying a predetermined correspondence relationship between the steering angle θi, which is the steering position of the steered wheels 5, and the steering angle θs, which is the rotational position of the steering wheel 3. The steering angle θs is an example of a steering signal. In other words, the process of calculating the steering angle θs in the CPU 60a is an example of a steering signal generation process.

[0044] On the other hand, in step 102, if the normal control preparation process is being executed (step 102: NO), the steering CPU determines whether or not a timeout has occurred (step 106). In step 106, the steering CPU determines whether or not the elapsed time since the start of the normal control preparation process has exceeded an upper limit time that satisfies the timeout condition. The upper limit time is, for example, a value within a range in which the normal control preparation process on the steering side can be repeated multiple times.

[0045] Next, if the timeout condition is not met (step 106: NO), the steering CPU continues the processing of step 102, i.e., the execution of the normal control preparation processing. On the other hand, if the timeout condition is met (step 106: YES), the steering CPU cannot complete the startup processing, and therefore transitions to a function stop state in which the function of the steering control device 1 is stopped, etc.

[0046] <Regarding normal control preparation processing on the reaction force side> As shown in Fig. 4, in the reaction force side normal control preparation process, the CPU 50a determines whether necessary information is set in the memory 50b (step 202). In step 202, if the CPU 50a is unable to read out the reaction force reference value θns in the initial check process (step 100), it determines that necessary information is not set in the memory 50b. In the initial check process, the CPU 50a cannot read out the reaction force reference value θns if the reaction force reference value θns has not been internally set. For example, after the battery 47 is removed and replaced, the reaction force reference value θns is not internally set.

[0047] Next, if the CPU 50a can read the reaction force reference value θns in the initial check process (step 100) (step 202: NO), the CPU 50a ends the process and completes the normal control preparation process on the reaction force side. Completion of the reaction force side process is notified to the CPU 60a via the local network 49.

[0048] On the other hand, if the CPU 50a is unable to read out the reaction force reference value θns in the initial check process (step 100) (step 202: YES), it executes a control information setting process (step 204). In step 204, the control information setting process executed by the CPU 50a includes a process of referencing the rotation angle θa. The CPU 50a also includes an integrated rotation angle acquisition process for calculating a provisional steering angle θsi, which is an integrated value obtained using the position of the rotation angle θa at the time of power-on as a provisional reference value. The provisional steering angle θsi is the integrated rotation angle, i.e., the absolute rotation angle. The reaction force side control information setting process includes a learning process in which the CPU 50a acquires values ​​while rotating the steering wheel 3 to each of the left and right limit positions 3a, 3b.

[0049] For example, as shown in Fig. 5, in the learning process, the CPU 50a rotates the steering wheel 3 in one of the left and right directions, i.e., rightward as a first direction (step 402). In step 402, the CPU 50a executes feedback processing to make the temporary steering angle θsi follow the steering target angle θs*. The steering target angle θs* is a value that is updated so as to gradually change from the value of the temporary steering angle θsi at the start of the learning process to exceed the rightward limit position 3a. In this way, the CPU 50a calculates a control signal MSs for rotating the steering wheel 3 rightward.

[0050] Next, when the steering wheel 3 reaches the right limit position 3a, the CPU 50a temporarily stores the right limit position θrl (step 404). In step 404, the CPU 50a monitors, for example, the currents iu1, iv1, iw1, the steering torque Th, and the angular velocity ωs, which is the amount of change in the tentative steering angle θsi. In this way, the CPU 50a determines that the steering wheel 3 has reached the limit position 3a. The right limit position θrl is the tentative steering angle θsi when it is determined that the steering wheel 3 has reached the right limit position 3a.

[0051] Next, the CPU 50a rotates the steering wheel 3 to the other side to the right, i.e., to the left, which is the second direction (step 406). In step 406, the CPU 50a executes feedback processing to make the temporary steering angle θsi follow the steering target angle θs*, similar to the processing in step 402 for rotating the steering wheel 3 to the right. The steering target angle θs* is a value that is updated so as to gradually change from the value of the temporary steering angle θsi when the right limit position 3a is reached to exceed the right limit position 3a. In this way, the CPU 50a calculates a control signal MSs for rotating the steering wheel 3 to the left.

[0052] Next, when the steering wheel 3 reaches the left limit position 3b, the CPU 50a temporarily stores the left limit position θ11 (step 408). In step 408, similar to step 404 when the steering wheel 3 reaches the right limit position 3a, the CPU 50a monitors, for example, the currents iu1, iv1, iw1, the steering torque Th, and the angular velocity ωs, which is the amount of change in the provisional steering angle θsi. In this way, the CPU 50a determines that the steering wheel 3 has reached the limit position 3b. The left limit position θ11 is the provisional steering angle θsi when it is determined that the steering wheel 3 has reached the left limit position 3b.

[0053] Next, the CPU 50a calculates a value corresponding to half the sum of the temporarily stored right limit position θrl and left limit position θll as the reaction force midpoint value θcs (step 410), and writes and sets the reaction force midpoint value θcs as the reaction force reference value θns (step 412). After that, the CPU 50a completes setting of the reaction force reference value θns, thereby terminating the learning process and completing the reaction force side normal control preparation process. Completion of the reaction force side process is notified to the CPU 60a via the local network 49. Note that during the learning process, the CPU 50a outputs steering information Ss including a provisional steering angle θsi instead of the steering angle θs to the steering control unit 60 via the local network 49. The provisional steering angle θsi is an example of a steering signal. In other words, the process of calculating the provisional steering angle θsi in the CPU 50a is an example of a steering signal generation process.

[0054] If the CPU 50a does not complete setting of the reaction force reference value θns, the CPU 50a will eventually satisfy the timeout condition (step 106: YES) and transition to a function-stopped state. Also, if the CPU 50a is not notified of the completion of the steering-side processing, the CPU 50a will eventually satisfy the timeout condition (step 106: YES) and transition to a function-stopped state.

[0055] <Regarding normal control preparation processing for steering> As shown in Fig. 6, in the normal control preparation process for the steering side, the CPU 60a determines whether or not necessary information is set in the memory 60b (step 302). In step 302, the CPU 60a determines that the reaction force reference value θns cannot be read in the reaction force side initial check process (step 100), similar to the process in step 202. This causes the CPU 60a to determine whether or not it is necessary to execute the control information setting process for the reaction force side.

[0056] Next, when CPU 60a determines that it is not necessary to execute the control information setting process on the reaction force side (step 302: NO), it ends the process and completes the normal control preparation process on the turning side. Completion of the process on the turning side is notified to CPU 50a via local network 49.

[0057] On the other hand, when CPU 60a determines that it is necessary to execute the control information setting process on the reaction force side (step 302: YES), it executes steering unit abnormality determination process to determine whether or not there is a mechanical abnormality in steering unit 6 (step 304). In a situation where the steering unit abnormality determination process is executed, the control information setting process (step 204) is being executed on the reaction force side. For example, the timing at which CPU 60a starts the steering unit abnormality determination process coincides with the timing at which the control information setting process is started on the reaction force side.

[0058] The CPU 60a also includes a dead-zone setting process that sets a dead-zone so as not to control the state of the steering unit 6, i.e., the pinion angle θp, with respect to the temporary steering angle θsi included in the steering information Ss while the control information setting process is being executed on the reaction force side. The dead-zone setting process includes a process that calculates a target pinion angle θp* corresponding to the temporary steering angle θsi based on the temporary steering angle θsi included in the steering information Ss. The dead-zone setting process includes a process that limits the value of the control amount obtained as a result of feedback processing that causes the pinion angle θp to follow the target pinion angle θp* to a guard value L. The guard value L is, for example, "0." As a result, the CPU 60a calculates the control signal MSt so as not to change the pinion angle θp.

[0059] In contrast, as shown in FIG. 7, the steering unit abnormality determination process executed by the CPU 60a includes a process of temporarily reducing the dead zone during the execution of the dead zone setting process. More specifically, the CPU 60a changes the guard value L to the relaxation value Lr (step 502). In step 502, the CPU 60a increases the absolute value of the guard value L by changing the guard value L to the relaxation value Lr. The relaxation value Lr is set, for example, to a value greater than "0" and within a range that allows the steering angle θi of the steered wheels 5 to change by a few degrees. The relaxation value Lr is set, for example, taking into consideration the frictional force between the steered wheels 5 and the road surface and play, which is a mechanical tolerance. Changing the guard value L to the relaxation value Lr relaxes the restriction imposed by the guard value L. This reduces the dead zone, which is used to prevent the state of the steering unit 6, i.e., the pinion angle θp, from being controlled with respect to the provisional steering angle θsi included in the steering information Ss. As a result, while the control information setting process is being executed on the reaction force side, the CPU 60a calculates a control signal MSt corresponding to the control amount, which is the relaxation value Lr, while the provisional steering angle θsi included in the steering information Ss changes in connection with the learning process.

[0060] Next, the CPU 60a determines whether the pinion angle θp has changed while operating the steering unit 6 by calculating the control signal MSt (step 504). In step 504, the CPU 60a monitors whether the pinion angle θp has changed by, for example, an angle corresponding to several degrees of the steering angle θi of the steered wheels 5, thereby determining whether the steering unit 6 is operating normally, i.e., whether there is a mechanical abnormality. In other words, if the CPU 60a determines that the pinion angle θp has changed (step 504: YES), it determines that there is no mechanical abnormality in the steering unit 6. On the other hand, if the CPU 60a determines that the pinion angle θp has not changed (step 504: NO), it determines that there is a mechanical abnormality in the steering unit 6.

[0061] Next, when CPU 60a determines that pinion angle θp has changed (step 504: YES), it determines that there is no mechanical abnormality in steering unit 6 and restores guard value L from relaxation value Lr to its original value (step 506). In step 506, CPU 60a reduces the absolute value of guard value L, for example, by restoring guard value L to "0." In other words, CPU 60a temporarily relaxes the restriction imposed by guard value L by temporarily increasing the absolute value of guard value L during steering unit abnormality determination processing. Thereafter, CPU 60a completes steering unit abnormality determination processing and completes steering-side normal control preparation processing. Completion of steering-side processing is notified to CPU 50a via local network 49. Note that the time required for CPU 60a to perform steering unit abnormality determination processing is sufficiently shorter than the time required for reaction-force side control information setting processing. In other words, the steering unit abnormality determination process is a process that is executed during part of the execution of the control information setting process on the reaction force side, and is completed before the control information setting process on the reaction force side ends.

[0062] On the other hand, if the CPU 60a determines that the pinion angle θp has not changed (step 504: NO), the CPU 60a determines that there is a mechanical abnormality in the steering unit 6 and sets a fail state (step 508). In step 508, the CPU 60a includes processing for notifying other control devices mounted on the vehicle that it has determined that there is a mechanical abnormality in the steering unit 6. The other control devices control the operation of, for example, a warning or other display device that notifies the driver by visually appealing to the driver. Examples of display devices include a head-up display (HUD), an instrument panel, a navigation system display, and an LED (light emitting diode). When notifying that it has determined that there is a mechanical abnormality in the steering unit 6, the CPU 60a once sets a fail state and notifies the other control devices mounted on the vehicle without interruption as long as the power is on, even if the power is off in between.

[0063] If the CPU 60a sets the fail state, the CPU 60a transitions to the function stop state. Also, if the CPU 60a is not notified of the completion of the reaction force side processing, the CPU 60a will eventually transition to the function stop state by satisfying the timeout condition (step 106: YES).

[0064] <Operation of this embodiment> For example, as shown in Fig. 8(a), on the reaction force side, the startup process starts when the power is turned on, and the control information setting process is executed. After that, on the reaction force side, the steering angle synchronization process is executed, and when the startup process is completed, the control for steering the vehicle traveling, that is, the execution of the normal reaction force process, becomes possible.

[0065] For example, as shown in Figure 8(b), on the steering side, startup processing is started when the power is turned on, and steering unit abnormality detection processing is started in conjunction with the start of control information setting processing on the reaction force side. After that, on the steering side, by completing the startup processing, it becomes possible to control steering of the vehicle, i.e., to execute normal steering processing.

[0066] The steering unit abnormality determination process executed by CPU 60a of steering control unit 60 is executed while vehicle steering system 2 has not yet transitioned to a normal control state after power is turned on, i.e., while startup processing is being executed. While startup processing is being executed, control of steering the vehicle's travel is not possible, and the vehicle is therefore in a state in which it cannot travel. In a situation in which the vehicle cannot travel, the occurrence of unintended behavior, such as the vehicle traveling in an unintended direction, is suppressed even if steering unit 6 is operated to determine whether or not there is an abnormality.

[0067] <Effects of this embodiment> (1-1) By executing the steering unit abnormality determination process during execution of the startup process, the occurrence of unintended behavior such as the vehicle traveling in an unintended direction is suppressed even if the steering unit 6 is operated to determine whether or not there is an abnormality. This ensures the safety of the driver even if the steering unit 6 is operated to determine whether or not there is an abnormality. Therefore, in a steer-by-wire steering device, a mechanical abnormality in the steering unit 6 can be detected.

[0068] (1-2) While the startup process is being executed, the driver is in a state of waiting to drive. For example, if the steering unit abnormality determination process is executed at a timing other than the execution of the startup process, the state of waiting for the driver to drive will be extended by the time the steering unit abnormality determination process is executed. In contrast, by executing the steering unit abnormality determination process while the startup process is being executed, the state of waiting for the driver to drive will be prevented from being extended.

[0069] (1-3) The reaction force side startup processing includes a control information setting processing for setting the reaction force reference value θns while controlling the operation of the steering unit 4 so as to rotate the steering wheel 3. The turning unit abnormality determination processing is executed while the steering wheel 3 is being rotated in the reaction force side startup processing. While the reaction force side control information setting processing is being executed, the rotation of the steering wheel 3 makes it possible for the driver to recognize that the vehicle is in a standby state before driving. While the driver is being made aware that the vehicle is in a standby state before driving, it is possible to make it difficult for the driver to recognize that the steered wheels 5 have been turned through the turning unit abnormality determination processing. Therefore, it is possible to make it difficult for the driver to feel uncomfortable regarding the execution of the turning unit abnormality determination processing.

[0070] (1-4) The processing related to the control of steering the vehicle includes a processing executed by the CPU 50a to calculate the steering angle θs and a processing executed by the CPU 60a to control the state of the steering unit 6 so that the state corresponds to the steering angle θs. After the vehicle steering system 2 is powered on, the CPU 50a calculates the provisional steering angle θsi while the control information setting processing is being executed on the reaction force side. Furthermore, the processing executed by the CPU 60a to control the state of the steering unit 6 includes a guard processing to prevent the state of the steering unit 6 from being controlled with respect to the provisional steering angle θsi while the control information setting processing is being executed on the reaction force side. The guard processing includes a processing to temporarily reduce the dead zone while the steering unit abnormality determination processing is being executed. Therefore, the processing related to the control of steering the vehicle can be diverted for the steering unit abnormality determination processing. This allows the scale of design changes to be kept small even when the steering unit abnormality determination processing is executed.

[0071] (1-5) The guard processing sets a dead zone by limiting the value of the control amount for controlling the state of the steering unit 6 with respect to the tentative steering angle θsi to the guard value L. The dead zone is temporarily narrowed by changing the guard value L to the relaxation value Lr, thereby relaxing the restriction imposed by the guard value L. This makes it easy to make design changes even when the steering unit abnormality determination processing is executed. This is effective in keeping the scale of the design changes small.

[0072] <Second embodiment> The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. For ease of explanation, the same components as those in the first embodiment will be assigned the same reference numerals as those in the first embodiment, and the description thereof will be omitted.

[0073] The CPU 60a of the steering control unit 60 of this embodiment is configured so that the steering unit abnormality determination process is performed on the condition that the steering wheel 3 needs to be rotated in the steering angle synchronization process.

[0074] 9, in the steering angle synchronization process on the steering side, the CPU 60a determines whether or not it is necessary to rotate the steering wheel 3 in the steering angle synchronization process (step 602). In step 602, the CPU 60a monitors whether or not the steering angle θs and the pinion angle θp deviate from a predetermined correspondence relationship. As a result, the CPU 60a determines whether or not the steering wheel 3 is being rotated through the reaction force side steering angle synchronization process.

[0075] Subsequently, when the CPU 60a determines through the reaction force side steering angle synchronization process that the steering wheel 3 is not in a state of being rotated (step 602: NO), the CPU 60a ends the process.

[0076] On the other hand, when the CPU 60a determines that the steering wheel 3 is being rotated through the reaction force side steering angle synchronization processing (step 602: YES), it executes the steering unit abnormality determination processing (step 604). In this embodiment, the situation in which the steering unit abnormality determination processing is executed is one in which processing is being executed to rotate the steering wheel 3 through the reaction force side steering angle synchronization processing. For example, the timing at which the CPU 60a starts the steering unit abnormality determination processing coincides with the timing at which the steering wheel 3 starts to rotate through the reaction force side steering angle synchronization processing.

[0077] In the steering unit abnormality determination process, the CPU 60a executes processes corresponding to steps 502, 504, 506, and 508 shown in FIG. 7. That is, the CPU 60a executes processes such as changing the guard value L to the relaxation value Lr and determining whether the pinion angle θp has changed while operating the steering unit 6 by calculating a control signal MSt corresponding to the control amount that is the relaxation value Lr. In this case, since the reaction force side steering angle synchronization process is being executed, the CPU 60a calculates the control signal MSt corresponding to the control amount that is the relaxation value Lr while the steering angle θs included in the steering information Ss changes in connection with the reaction force side steering angle synchronization process. Then, the CPU 60a determines whether there is a mechanical abnormality in the steering unit 6 depending on whether the pinion angle θp has changed. In particular, if the CPU 60a determines that there is a mechanical abnormality in the steering unit 6, it sets a fail state and transitions to a function stop state.

[0078] According to the second embodiment described above, the same actions as those of the first embodiment can be obtained, and the same effects as those of (1-1) to (1-5) of the first embodiment can be obtained. Furthermore, according to the second embodiment, the following actions and effects can be obtained.

[0079] (2-1) For example, as shown in FIG. 10(a), if the reaction force reference value θns can be read out in the initial check process (step 100) on the reaction force side, the control information setting process is not executed. Therefore, the steering angle synchronization process is executed on the reaction force side without executing the control information setting process. In other words, the steering angle synchronization process (step 104) is executed on the reaction force side regardless of whether the control information setting process is executed or not. In this case, the steering wheel 3 is rotated on the reaction force side depending on the situation. Thereafter, the steering angle synchronization process is executed on the reaction force side, and the startup process is completed, thereby enabling control to steer the vehicle, i.e., execution of normal reaction force process.

[0080] For example, as shown in Fig. 10(b), on the steering side, the steering unit abnormality detection process is executed in synchronization with the start of rotation of the steering wheel 3 through the reaction force side steering angle synchronization process. After that, on the steering side, the startup process is completed, and control for steering the vehicle's running, that is, normal steering process can be executed.

[0081] As a result, in a situation where the steering wheel 3 is rotated through the reaction force side steering angle synchronization process, the turning unit abnormality detection process is executed even if the control information setting process is not executed on the reaction force side. Therefore, it is possible to increase the opportunities for the turning unit abnormality detection process to be executed. This is effective in improving the accuracy of detecting mechanical abnormalities in the turning unit 6.

[0082] <Other embodiments> The above-described embodiments may be modified as follows: In addition, the following other embodiments may be combined with each other within the scope of technical compatibility.

[0083] In the first embodiment, the steering unit abnormality detection process may be configured to be executed on the condition that the steering angle synchronization process requires the rotation of the steering wheel 3. According to the other embodiments described herein, it is possible to achieve the same effect as (2-1) of the second embodiment.

[0084] In each of the above embodiments, the dead zone setting process may be a process of limiting the value of the control amount obtained as a result of feedback processing that causes the pinion angle θp to follow the target pinion angle θp* by limiting the steering angle θs and the tentative steering angle θsi to guard values.

[0085] In each of the above embodiments, the dead zone setting process may be a process of receiving but invalidating the steering angle θs and the provisional steering angle θsi. In this case, the received steering angle θs and provisional steering angle θsi may be validated only while the steering unit abnormality detection process is being executed.

[0086] In each of the above embodiments, the dead zone setting process may be omitted. In this case, the steering unit abnormality detection process may include a process in which the CPU 60a calculates the target pinion angle θp* within a range that allows the steering angle θi of the steered wheels 5 to be changed by a few degrees.

[0087] In each of the above embodiments, the learning process may be a process in which the steering wheel 3 is first turned leftward, and then turned rightward.

[0088] In each of the above embodiments, the learning process may include a process for temporarily storing one of the limit positions θrl, θll. In other words, the process for the learning operation may not include a process for temporarily storing one of the limit positions θrl, θll. For example, if the process for temporarily storing the right limit position θrl is included, the reaction force CPU may calculate, as the reaction force midpoint value θcs, a value obtained by subtracting half the value of the rotation range between the right limit position 3a and the left limit position 3b from the right limit position θrl.

[0089] In each of the above embodiments, the learning process may include a process for determining the validity of the reaction force midpoint value θcs. In each of the above embodiments, the learning process may determine whether the steering wheel 3 has reached each limit position 3a or 3b by monitoring at least the currents iu1, iv1, and iw1. Furthermore, the learning process may determine whether the steering wheel 3 has reached each limit position 3a or 3b by taking into account other parameters in addition to the above embodiments. For example, the other parameters may include the amount of change in the currents iu1, iv1, and iw1, the amount of change in the angular velocity ωs, and the time since the steering wheel 3 started to rotate.

[0090] In each of the above embodiments, the normal control preparation process on the steering side may be configured to execute a learning process in which the CPU 60a acquires values ​​while the rack shaft 22, i.e., the steered wheels 5, are moved to the left and right rack ends 25. This allows the CPU 60a to detect mechanical abnormalities in the steering unit 6 while executing the learning process on the steering side.

[0091] In each of the above embodiments, the steering angle synchronization process may include a process of synchronizing the relative positions of the steering wheel 3 and the steerable wheels 5 by turning the steerable wheels 5. This allows the CPU 60a to detect a mechanical abnormality in the steering unit 6 while executing the steering angle synchronization process on the turning side.

[0092] In each of the above embodiments, the displacement amount of the steering wheel 3 is not limited to an amount calculated based on an integration process of the rotation angle θa. For example, it may be a value detected by a steering angle sensor that directly detects the rotation angle of the steering shaft 11. Note that the steering angle sensor may be provided, for example, on the steering shaft 11 between the steering wheel 3 and the torque sensor 41.

[0093] In each of the above embodiments, the steering actuator 12 does not necessarily have to include the steering-side reduction mechanism 14. In the above embodiments, reaction motor 13 is not limited to a three-phase brushless motor. For example, it may be a DC motor with brushes. The other embodiments described herein can be similarly applied to steering motor 32.

[0094] In each of the above embodiments, the pinion angle θp may be obtained by converting a detected value of the movement amount of the rack shaft 22. In this case, the control amount and the like related to the pinion angle θp are converted using the detected value of the movement amount of the rack shaft 22.

[0095] In each of the above embodiments, the operating member operated by the driver to steer the vehicle is not limited to the steering wheel 3. For example, it may be a joystick. In each of the above embodiments, steering unit 6 transmits the rotation of steering motor 32 to conversion mechanism 34 via transmission mechanism 33, but this is not limiting. For example, steering unit 6 may be configured so that the rotation of steering motor 32 is transmitted to conversion mechanism 34 via a gear mechanism. Also, steering unit 6 may be configured so that steering motor 32 directly rotates conversion mechanism 34. Furthermore, steering unit 6 may be configured to include a second rack-and-pinion mechanism, and so that the rotation of steering motor 32 is converted into reciprocating motion of rack shaft 22 by the second rack-and-pinion mechanism.

[0096] In each of the above embodiments, the steering unit 6 is not limited to a configuration in which the right steered wheels 5 and the left steered wheels 5 are linked together. In other words, the right steered wheels 5 and the left steered wheels 5 may be independently controlled.

[0097] In each of the above embodiments, the vehicle steering system 2 may be configured such that the power transmission path between the steering unit 4 and the steered unit 6 can be separated by a clutch, for example. [Explanation of symbols]

[0098] 1...Steering control device 2...Vehicle steering system 3...Steering wheel (steering member) 4...Steering unit 5...Steering wheel 6...Steering unit 50...Reaction force control unit 50a…CPU 60...Steering control unit 60a…CPU

Claims

1. A steering control device applied to a vehicle steering system that steers the running of a vehicle, the vehicle steering system includes a steer-by-wire steering device having a structure in which power transmission paths between a steering unit steered by a steering member of the vehicle and a steering unit that operates to steer steered wheels of the vehicle are separated, The steering control device is configured to execute a startup process and a steering unit abnormality determination process, the startup processing is processing for enabling control of steering the vehicle after the vehicle steering system is powered on, the steering unit abnormality determination process is a process for determining whether or not there is a mechanical abnormality in the steering unit while controlling the operation of the steering unit during execution of the startup process after the vehicle steering system is powered on, A steering control device configured so that control of steering the vehicle's travel cannot be performed if the steering unit abnormality determination process determines that there is a mechanical abnormality in the steering unit, and can be performed if the steering unit abnormality determination process determines that there is no mechanical abnormality in the steering unit.

2. the startup processing includes processing for controlling the operation of the steering unit, 2. The steering control device according to claim 1, wherein the steering unit abnormality determination process is executed while the operation of the steering unit is being controlled in the startup process.

3. 3. The steering control device according to claim 2, wherein the startup process includes a process of controlling the operation of the steering unit so as to rotate a steering wheel, which is the steering member, to a limit position in a first direction or a second direction.

4. 3. The steering control device according to claim 2, wherein the startup process includes a process for controlling the operation of the steering unit so that the rotational position of the steering wheel, which is the steering member, matches the steered position of the steered wheels obtained through the steering unit.

5. the processing related to the control of steering the traveling of the vehicle includes processing of calculating a steering signal indicating a state of the steering unit, and processing of controlling a state of the steering unit so as to be in a state corresponding to the steering signal, The process of calculating the steering signal is a process that is executed even during the startup process after the power supply of the vehicle steering system is turned on, the processing for controlling the state of the steering unit includes a dead zone setting processing for setting a dead zone so that the state of the steering unit is not controlled in response to the steering signal during execution of the startup processing after the vehicle steering system is powered on, 2. The steering control device according to claim 1, wherein the dead zone setting process includes a process of temporarily reducing the dead zone while the steering unit abnormality determination process is being executed.

6. 6. The steering control device according to claim 5, wherein the dead zone setting process is a guard process that sets the dead zone by limiting the value of a control variable for controlling the state of the steering unit in response to the steering signal to a guard value, and temporarily reducing the dead zone is a relaxation of the restriction imposed by the guard value.

7. A steering control method applied to a vehicle steering system for steering a vehicle that is equipped with a steer-by-wire steering device having a structure in which a power transmission path between a steering unit steered by a steering member of the vehicle and a steering unit that operates to steer steered wheels of the vehicle is separated, the method comprising: The steering control method includes executing a startup process and a steering unit abnormality determination process, the startup process is executed to enable control of steering the vehicle after the vehicle steering system is powered on; the steering unit abnormality determination process is executed during execution of the startup process after the vehicle steering system is powered on, to determine whether or not there is a mechanical abnormality in the steering unit while controlling the operation of the steering unit, A steering control method in which control of steering the vehicle's travel cannot be performed if the steering unit abnormality determination process determines that there is a mechanical abnormality in the steering unit, and can be performed if the steering unit abnormality determination process determines that there is no mechanical abnormality in the steering unit.

Images