Steering control device and steering control method

Abstract

The invention relates to a steering control device and a steering control method. A steering control device (1) is provided with a processor (50a) that controls a steering unit (4) that uses a reaction force motor (13) as a drive source. The processor (50a) is configured to execute an integrated rotation angle acquisition process for acquiring an integrated rotation angle, which is an integrated value of a rotation angle of the steering shaft (11), on the basis of a detection result of the angle sensor (42). The processor (50a) is configured to execute an abnormality determination process that determines whether an abnormality condition for detecting an abnormality of the stopper mechanism (11b) is satisfied based on the cumulative rotation angle. The abnormality determination process includes a process that determines that an abnormality condition is satisfied when the processor (50a) can determine that the cumulative rotation angle exceeds the limited rotation amount.

Description

Technical Field

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

[0002] For example, Japanese Unexamined Patent Application Publication No. 2020-69844 describes a vehicle steering system in which a steering unit and a steering unit are mechanically separated. In such a vehicle steering system, the rotation range of a steering shaft included in the steering unit is not limited by the steering unit mechanically separated from the steering unit. Therefore, the steering unit includes a stop mechanism for mechanically limiting the rotation range of the steering shaft. Summary of the invention

[0003] In the above steering system, for example, when the stop mechanism becomes unable to mechanically limit the rotation range of the steering shaft, the problem of the steering shaft continuing to rotate without limit occurs. To solve this problem, it is desirable to detect at an early stage that the rotation range of the steering shaft cannot be mechanically limited.

[0004] A steering control device according to a first aspect of the present invention is applied to a vehicle steering system, the vehicle steering system having a structure in which a power transmission path between a steering unit and a steering unit is cut off, the steering unit being configured to be steered by a steering wheel of a vehicle, the steering unit being configured to operate to steer a steering wheel of a vehicle, the steering unit comprising: a steering shaft connected to the steering wheel; a reaction force motor configured to apply a motor torque to the steering shaft to apply a steering reaction force to the steering wheel; a stop mechanism configured to adjust the rotation of the steering shaft in the left-right direction to within a limited rotation amount; and an angle sensor configured to detect the rotation angle of the steering shaft. The steering control device includes a processor that controls the steering unit, the steering unit using the reaction force motor as a drive source. The processor is configured to execute the following processing: a cumulative rotation angle acquisition processing of acquiring a cumulative rotation angle based on a detection result of the angle sensor, the cumulative rotation angle being a cumulative value of the rotation angle of the steering shaft; and an abnormality determination processing of determining whether an abnormal condition is satisfied based on the cumulative rotation angle, the abnormal condition being a condition for detecting an abnormality of the stopper mechanism. The abnormality determination processing includes a process of determining that the abnormal condition is satisfied when the processor is able to determine that the cumulative rotation angle exceeds a limit rotation amount.

[0005] In the above configuration, the processor includes an abnormality determination process for detecting an abnormality of the stopper mechanism using software. Thus, in the vehicle steering system, for example, even in the case where the stopper mechanism becomes unable to mechanically limit the rotation range of the steering shaft, early detection can be performed. Therefore, even in the case where such a problem that the steering shaft continues to rotate without restriction occurs, such a problem can be dealt with at an early stage.

[0006] In the steering control device according to the first aspect of the present invention, the cumulative rotation angle acquisition processing may include: a processing of acquiring a first absolute rotation angle, which is a cumulative rotation angle relative to the reference value, in a first state in which a reference value indicating a neutral position of a steering wheel has been internally set; and a processing of acquiring a second absolute rotation angle, which is a cumulative rotation angle in which the reference value is not used as a reference, in a second state in which the reference value has not been internally set. The abnormality determination processing may include: a first abnormality determination processing of determining that an abnormal condition is satisfied in the first state based on the first absolute rotation angle; and a second abnormality determination processing of determining that an abnormal condition is satisfied in the second state based on the second absolute rotation angle.

[0007] In the above configuration, the processor includes processing in which the satisfaction requirement of the abnormal condition is different depending on whether the state is the first state or the second state. Thus, in the vehicle steering system in which the first state and the second state can be set, it is possible to appropriately determine that the cumulative rotation angle exceeds the limit rotation amount regardless of the state. Therefore, it is possible to detect an abnormality of the stopper mechanism at an early stage regardless of whether the reference value has been internally set.

[0008] In the steering control device according to the first aspect of the present invention, the first abnormality determination process may be a process for determining that an abnormal condition is satisfied when the processor is able to determine that the magnitude of the first absolute rotation angle is equal to or greater than a first threshold value. The first threshold value may be a value equal to or greater than half of the limited rotation amount. The second abnormality determination process may be a process for determining that an abnormal condition is satisfied when the processor is able to determine that the magnitude of the second absolute rotation angle is equal to or greater than a second threshold value. The second threshold value may be a value equal to or greater than the limited rotation amount.

[0009] In the above configuration, in the first abnormality determination process, when determining the size of the first absolute rotation angle in the first state, the first threshold is used, and thus the abnormality of the stopper mechanism can be appropriately determined. On the other hand, in the second abnormality determination process, when determining the size of the second absolute rotation angle in the second state, a second threshold different from the first threshold is used, and thus the abnormality of the stopper mechanism can be appropriately determined. Thus, determination can be performed based on the first state and the second state.

[0010] In the steering control device according to the first aspect of the present invention, the steering unit may include a locking mechanism configured to mechanically lock the rotation of the steering shaft. The second state may be a state to which the steering control device transitions from a state in which the locking mechanism locks the rotation of the steering shaft. The first state includes a state to which the steering control device transitions after the second state. The second threshold value may be a value for which the first threshold value and an adjustment amount at least related to the configuration of the locking mechanism are taken into account.

[0011] For example, as an assumed initial state of the steering wheel in the second state, a situation in which the steering wheel rotates until just before transitioning to the state corresponding to the first threshold value is possible. In this case, when the locking mechanism locks the rotation of the steering shaft, it can be assumed that the steering wheel rotates more than the first threshold value due to the configuration of the locking mechanism. However, the second threshold value is a value for which an adjustment amount related to the configuration of the locking mechanism is taken into account. Thus, an abnormality of the stop mechanism can be appropriately detected.

[0012] In the steering control device according to the first aspect of the present invention, the reference value may be a value acquired through a learning operation in which the steering shaft is moved to a limit position in a first direction and a limit position in a second direction. The processor may be configured to perform a learning process in the second state, the learning process being a process for internally setting the reference value through the learning operation. The learning process may include: during the learning operation, a process of acquiring a first limit position and a second limit position, the first limit position being an angle corresponding to a position of the steering shaft at a limit position in the first direction, the second limit position being an angle corresponding to a position of the steering shaft at a limit position in the second direction; and a process of setting the reference value based on the limit position acquired for each direction.

[0013] In the above configuration, even during the learning operation, abnormality of the stopper mechanism can be appropriately detected.

[0014] The steering control method according to the second aspect of the present invention is a method applied to a vehicle steering system, the vehicle steering system having a structure in which a power transmission path between a steering unit and a steering unit is cut off, the steering unit being configured to be steered by a steering wheel of the vehicle, the steering unit being configured to operate to steer a steering wheel of the vehicle. The steering control method includes controlling a steering unit by a processor, the steering unit using a reaction force motor as a driving source, the reaction force motor being configured to apply a motor torque to a steering shaft connected to the steering wheel to apply a steering reaction force to the steering wheel. Controlling the steering unit by the processor includes: acquiring a cumulative rotation angle based on a detection result of an angle sensor, the angle sensor being configured to detect a rotation angle of the steering shaft, the cumulative rotation angle being an accumulated value of the rotation angle of the steering shaft; and determining whether an abnormal condition is satisfied based on the cumulative rotation angle, the abnormal condition being a condition for detecting an abnormality of a stop mechanism, the stop mechanism being configured to adjust the rotation of the steering shaft in the left-right direction to within a limited rotation amount. Determining whether the abnormal condition is satisfied includes determining that the abnormal condition is satisfied when the processor is able to determine that the cumulative rotation angle exceeds the limited rotation amount.

[0015] With the steering control device according to the first aspect of the invention and the steering control method according to the second aspect of the invention, even in the event that such a problem occurs that the steering shaft continues to rotate without limit, such a problem can be dealt with at an early stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals denote like elements, and in which:

[0017] Figure 1 is a diagram showing the configuration of a steer-by-wire type steering device according to an embodiment;

[0018] Figure 2 It is shown Figure 1 A block diagram of the electrical configuration of the steering control device in FIG.

[0019] Figure 3 is a flow chart for describing the processing procedure of terminal output processing;

[0020] Figure 4 is a flow chart for describing the processing procedure of the learning process;

[0021] Figure 5 is a flowchart for describing a processing procedure of a first abnormality detection process;

[0022] Figure 6is a flowchart for describing a processing procedure of a second abnormality detection process; and

[0023] Figure 7 is a diagram for describing the first threshold value and the second threshold value. DETAILED DESCRIPTION

[0024] A steering control device according to an embodiment will be described.

[0025] The vehicle steering system 2 includes a steering control device 1. The vehicle steering system 2 includes a steering unit 4 and a steering unit 6. The steering unit 4 is steered by the driver through a steering wheel 3 of the vehicle as a steering member. The steering unit 6 steers the right steering wheel 5 and the left steering wheel 5 of the vehicle in response to the steering input to the steering unit 4 by the driver. For example, the vehicle steering system 2 in the embodiment has a structure in which the power transmission path between the steering unit 4 and the steering unit 6 is always mechanically cut off. The power transmission path between the steering actuator 12 described later and the steering actuator 31 described later is always mechanically cut off. That is, the vehicle steering system 2 includes a steer-by-wire type steering device.

[0026] The steering unit 4 includes a steering shaft 11, a steering actuator 12, a spiral cable mechanism, and a locking mechanism 16. The steering shaft 11 is coupled to the steering wheel 3. At an end portion 11a of the steering shaft 11, a stopper mechanism 11b is provided, the end portion 11a being on the opposite side of the side where the steering shaft 11 is coupled to the steering wheel 3. The stopper mechanism 11b specifies the rotation range of the steering shaft 11. Therefore, the rotation range of the steering wheel 3 that rotates integrally with the steering shaft 11 is specified by the stopper mechanism 11b. For example, the steering wheel 3 can be rotated within the limited rotation amount θ1 so that the rotation range is a range between a rightward limited position 3a and a leftward limited position 3b.

[0027] The steering actuator 12 includes a reaction force motor 13 and a steering side speed reduction mechanism 14. The reaction force motor 13 is a steering side motor that applies a steering reaction force as a force resisting the steering of the steering wheel 3 to the steering wheel 3 through the steering shaft 11. For example, the reaction force motor 13 is connected to the steering shaft 11 through the steering side speed reduction mechanism 14 composed of a worm and a worm wheel. For example, a three-phase brushless motor is used as the reaction force motor 13 in the embodiment.

[0028] The spiral cable mechanism is connected to the steering wheel 3. The spiral cable mechanism includes a first housing 15a, a second housing 15b, a tubular member 15c and a spiral cable 15d. The first housing 15a is fixed to the steering wheel 3. The second housing 15b is fixed to the vehicle body. The tubular member 15c is fixed to the second housing 15b and is accommodated in a space formed by the first housing 15a and the second housing 15b. The spiral cable 15d is wound around the tubular member 15c. The steering shaft 11 is inserted into the tubular member 15c. For example, the spiral cable 15d is an electric wire that connects the horn, airbag, etc. fixed to the steering wheel 3 to the battery 47, etc. The total length Lca of the spiral cable 15d is sufficiently long compared to the distance from the horn, airbag, etc. to the battery 47. Within a range corresponding to the total length Lca, the steering wheel 3 is allowed to rotate, and power is supplied to the horn, airbag, etc. Furthermore, the total length Lca of the spiral cable 15 d is sufficiently longer than the rotation range between the rightward limit position 3 a and the leftward limit position 3 b in the stopper mechanism 11 b , that is, the limit rotation amount θ1 of the steering wheel 3 .

[0029] The locking mechanism 16 is a mechanism for mechanically adjusting the rotation of the steering wheel 3. For example, the locking mechanism 16 includes a motor and a locking rod. The locking rod moves between a locking position and an unlocking position as the motor rotates. The locking position is a position of the locking rod in which the locking rod cooperates with the gear portion of the steering shaft 11. When the locking rod is in the locking position, the locking mechanism 16 is in a locked state that restricts the rotation of the steering wheel 3. The unlocking position is a position of the locking rod in which the cooperation with the gear portion of the steering shaft 11 is released. When the locking rod is in the unlocking position, the locking mechanism 16 is in an unlocking state that allows the steering wheel 3 to rotate.

[0030] The steering unit 6 includes a pinion shaft 21, a rack shaft 22, and a rack housing 23. The pinion shaft 21 and the rack shaft 22 are coupled to each other at a predetermined crossing angle. Pinion teeth 21a formed on the pinion shaft 21 mesh with rack teeth 22a formed on the rack shaft 22, thereby constituting a rack-and-pinion mechanism 24. The pinion shaft 21 corresponds to a rotation axis that allows conversion into a steering angle as a steering position of the steering wheel 5. The rack housing 23 accommodates the rack-and-pinion mechanism 24.

[0031] One end of the pinion shaft 21 on the opposite side to the side where the pinion shaft 21 is coupled to the rack shaft 22 protrudes from the rack housing 23. Both ends of the rack shaft 22 protrude from both ends of the rack housing 23 in the axial direction of the rack housing 23. The tie rod 26 is coupled to both ends of the rack shaft 22 through the rack ends 25, each of which is a ball joint. The distal end of the tie rod 26 is coupled to a steering knuckle not shown to which the right and left steering wheels 5, 5 are attached, respectively.

[0032] 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 for steering the steering wheel 5 to the rack shaft 22 through the transmission mechanism 33 and the conversion mechanism 34. For example, the steering motor 32 transmits the rotation to the conversion mechanism 34 through the transmission mechanism 33 as a belt transmission mechanism. For example, the transmission mechanism 33 converts the rotation of the steering motor 32 into the reciprocating motion of the rack shaft 22 through the conversion mechanism 34 as a ball screw mechanism. For example, a three-phase brushless motor is used as the steering motor 32 in the embodiment.

[0033] In the vehicle steering system 2, in response to the driver's steering manipulation of the steering wheel 3, the motor torque is applied from the steering actuator 31 to the rack shaft 22 as a steering force, thereby changing the steering angle of the steering wheel 5. At this time, a steering reaction force resisting the driver's steering manipulation is applied from the steering actuator 12 to the steering wheel 3. Thus, in the vehicle steering system 2, the steering torque Th required for the steering manipulation of the steering wheel 3 is changed by the steering reaction force as the motor torque applied from the steering actuator 12.

[0034] The reason why the pinion shaft 21 is provided is because the rack shaft 22 is supported inside the rack housing 23 together with the pinion shaft 21. The rack shaft 22 is supported to be movable in the axial direction of the rack shaft 22 and pressed to the pinion shaft 21 by a support mechanism not shown provided in the vehicle steering system 2. Thus, the rack shaft 22 is supported inside the rack housing 23. Instead of using the pinion shaft 21, another support mechanism for supporting the rack shaft 22 in the rack housing 23 may be provided.

[0035] Electrical configuration of steering control device

[0036] like Figure 1 As shown, 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 the respective motors 13,32.

[0037] Detection results of the various sensors are input to the steering control device 1 . Examples of the various sensors include a torque sensor 41 , a steering-side rotation angle sensor 42 , a steering-side rotation angle sensor 43 , and a vehicle speed sensor 44 .

[0038] The torque sensor 41 is provided at a portion of the steering shaft 11 between the steering wheel 3 and the steering-side speed reduction mechanism 14. The torque sensor 41 detects a steering torque Th, which is a value indicating a torque applied to the steering shaft 11 by the driver's steering of the steering wheel 3. The steering torque Th is detected based on the twisting of a torsion bar 41a, which is located in the middle of the steering shaft 11 and is provided in the steering shaft 11 between the steering wheel 3 and the steering-side speed reduction mechanism 14. The steering-side rotation angle sensor 42 is provided at the reaction motor 13. The steering-side rotation angle sensor 42 detects a rotation angle θa, which is a rotation angle of a rotation shaft of the reaction motor 13 and is an angle within 360 degrees. The steering-side rotation angle sensor 43 is provided at the steering motor 32. The steering-side rotation angle sensor 43 detects a rotation angle θb, which is a rotation angle of a rotation shaft of the steering motor 32 and is an angle within 360 degrees. The vehicle speed sensor 44 detects a vehicle speed V which is a traveling speed of the vehicle. In the embodiment, the steering-side rotation angle sensor 42 is an example of an angle sensor.

[0039] The power supply system 46 is connected to the steering control device 1. The power supply system 46 includes a battery 47. The battery 47 is a secondary battery equipped in the vehicle, and is a power supply to which electric power for operating the reaction force motor 13 and the steering motor 32 is supplied. In addition, the battery 47 is a power supply to which electric power for operating the locking mechanism 16 is supplied. In addition, the battery 47 is a power supply to which electric power for operating the steering control device 1 is supplied.

[0040] A vehicle start switch 48 (eg, an ignition switch) is provided between the steering control device 1 and the battery 47. Figure 14. The start switch 48 is provided in the middle of the power supply line L2, which is one of the two power supply lines L1 and L2 connecting the steering control device 1 and the battery 47 and is separated from the power supply line L1. When various functions are started, the start switch 48 is manipulated so that the vehicle travel drive source such as the engine is activated and the vehicle can run. The electrical continuity of the power supply line L2 is turned on or off by manipulating the start switch 48. In the embodiment, the operating state of the vehicle steering system 2 is associated with the operating state of the vehicle. Although the power supply line L1 is basically electrically continuous at all times, as a function of the vehicle steering system 2, the electrical continuity of the power supply line L1 is indirectly turned on or off according to the operating state of the vehicle steering system 2. The operating state of the vehicle steering system 2 is associated with the on-off state of the electrical continuity of the power supply lines L1 and L2, which is the state of the supply power of the battery 47. In the operating state of the vehicle steering system 2, when the electrical continuity of the power supply lines L1 and L2 is turned on based on the manipulation of the start switch 48, the power is turned on. In the operating state of the vehicle steering system 2 , when the electrical continuity of the power supply lines L1 , L2 is disconnected based on the manipulation of the start switch 48 , the power supply is disconnected.

[0041] The locking mechanism 16 switches between a locked state and an unlocked state depending on whether the power is turned on or off. For example, when the power is turned off, the locking mechanism 16 changes to a locked state. In the locked state, the vehicle changes to a state where the vehicle is stopped. In addition, when the power is turned on, the locking mechanism 16 changes to an unlocked state. In the unlocked state, the vehicle changes to a state where the vehicle can travel.

[0042] Function of the steering control

[0043] like Figure 2As shown, the steering control device 1 includes a reaction force control unit 50 and a steering control unit 60. The reaction force control unit 50 controls the steering wheel 3 as a control object. In order to control the steering reaction force as a controlled variable of the control object, the reaction force control unit 50 controls the driving of the steering actuator 12, more specifically, controls the driving of the reaction force motor 13. The steering control unit 60 controls the rack shaft 22 as a control object. In order to control the steering force as a controlled variable of the control object, the steering control unit 60 controls the driving of the steering actuator 31, more specifically, controls the driving of the steering motor 32. For example, the reaction force control unit 50 and the steering control unit 60 transmit and receive information to and from each other through a local network 49 for serial communication or the like. The reaction force control unit 50 constitutes a reaction force system RS by combining with the steering unit 4. The steering control unit 60 constitutes a steering system TS by combining with the steering unit 6. In the embodiment, the process of controlling the driving of the reaction force motor 13 by the reaction force control unit 50 is an example of the reaction force control process.

[0044] The reaction force control unit 50 includes a central processing unit (hereinafter referred to as "CPU") 50a and a memory 50b. The CPU 50a executes a program stored in the memory 50b at a predetermined calculation cycle, and thus the reaction force control unit 50 performs various processes. The steering control unit 60 includes a central processing unit (hereinafter referred to as "CPU") 60a and a memory 60b. The CPU 60a executes a program stored in the memory 60b at a predetermined calculation cycle, and thus the steering control unit 60 performs various processes. The CPUs 50a, 60a and the memories 50b, 60b constitute a microcomputer as a processing circuit. The memories 50b, 60b include computer-readable media such as random access memories (RAM) and read-only memories (ROM). Implementing various processes by software is an example. The processing circuits included in the reaction force control unit 50 and the steering control unit 60 may be configured so that at least some of the processes are implemented by hardware circuits such as logic circuits.

[0045] The CPU 50a of the reaction force control unit 50 receives the steering torque Th, the vehicle speed V, the rotation angle θa, and the steering information St. The steering information St is information obtained from the steering control unit 60 through the local network 49. The CPU 50a calculates a control signal MSs for controlling the steering reaction force based on the steering torque Th, the vehicle speed V, the rotation angle θa, and the steering information St, and the control signal MSs is a signal to be output to the reaction force inverter 51. The reaction force inverter 51 is a drive circuit that converts the DC voltage of the battery 47 into an AC voltage and applies the AC voltage to the reaction force motor 13. In this case, the CPU 50a refers to the current iu1, iv1, iw1 flowing through the reaction force motor 13. The current iu1, iv1, iw1 is quantified as the voltage drop amount at the shunt resistor provided at each branch of the reaction force inverter 51. Thus, the CPU 50a controls the drive of the reaction force motor 13 so that a motor torque that causes the steering reaction force is generated.

[0046] The CPU 50a converts the rotation angle θa into a cumulative rotation angle, which is a cumulative value from the reaction force reference value θns stored in the memory 50b, that is, into an absolute rotation angle. The absolute rotation angle is a value converted in a range exceeding 360° by counting the number of times the reaction force motor 13 rotates from the reaction force reference value θns. For example, the reaction force reference value θns is a value indicating a straight-line moving state, which is a steering state of the steering wheel 3 when the vehicle moves straight. In the embodiment, the reaction force reference value θns is a value indicating a steering neutral position as a rotation position of the steering wheel 3 in the straight-line moving 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 factor based on the rotation speed ratio of the steering side speed reduction mechanism 14. The CPU 50a calculates the steering angle θs as an absolute angle relative to the steering neutral position, that is, the reaction force reference value θns. The steering angle θs obtained in this way is used to calculate the control signal MSs. The steering information Ss (eg, steering angle θs) used by the CPU 50 a is output to the steering control unit 60 via the local network 49 .

[0047] The CPU 60a of the steering control unit 60 receives the vehicle speed V, the rotation angle θb, and the steering manipulation information Ss. The steering manipulation information Ss is information obtained from the reaction force control unit 50 through the local network 49. The CPU 60a calculates a control signal MSt for controlling the steering force based on the vehicle speed V, the rotation angle θb, and the steering manipulation information Ss, and the control signal MSt is a signal to be output to the steering inverter 61. The steering inverter 61 is a drive circuit that converts the DC voltage of the battery 47 into an AC voltage and applies the AC voltage to the steering motor 32. In this case, the CPU 60a refers to the current iu2, iv2, iw2 flowing through the steering motor 32. The current iu2, iv2, iw2 is quantified as the voltage drop amount at the shunt resistor provided at each branch of the steering inverter 61. Thereby, the CPU 60a controls the driving of the steering motor 32 so that a motor torque that causes the steering force is generated.

[0048] The CPU 60a converts the rotation angle θb into a cumulative rotation angle, which is a cumulative value from the steering reference value θnt stored in the memory 60b, that is, into an absolute rotation angle. The absolute rotation angle is a value converted in a range exceeding 360° by counting the number of times the steering motor 32 rotates from the steering reference value θnt. For example, the steering reference value θnt is a value indicating a straight-line moving state, which is a steering state of the rack shaft 22 when the vehicle moves straight. In the embodiment, the steering reference value θnt is a value indicating a rack neutral position as a position of the rack shaft 22 in the straight-line moving 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 factor based on the rotation speed ratio of the transmission mechanism 33, the guidance of the conversion mechanism 34, and the rotation 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, that is, the steering reference value θnt. The pinion angle θp obtained in this way is used to calculate the control signal MSt. The steering information St (eg, the pinion angle θp) used by the CPU 60 a is output to the reaction force control unit 50 via the local network 49 .

[0049] CPU state transition of the reaction force control unit

[0050] After the start switch 48 is turned on and the power is turned on in the power off state, the CPU 50a performs an initial check process. According to whether the IG signal Sg output by the start switch 48 has been input, the CPU 50a determines whether the power is in the on state or the off state, and performs switching between the locked state and the unlocked state.

[0051] The initial check process includes a check process regarding the operation of the reaction force system RS, such as a check process regarding whether the CPU 50a and the memory 50b can operate normally. The initial check process includes a check process regarding the communication with the steering system TS, such as a check process regarding whether the steering information St can be input through the local network 49. The initial check process includes a process that enables the execution of the operation process for the steering manipulation unit 4, such as a process that reads various information from the memory 50b. The various information read from the memory 50b by the CPU 50a in the initial check process includes the content of the reaction force reference value θns.

[0052] In the initial check process, in the case where the CPU 50a can read the reaction force reference value θns, the CPU 50a transitions to the normal control state. In the initial check process, in the case where the reaction force reference value θns has been internally set, the CPU 50a can read the reaction force reference value θns. The normal control state is a state for performing a normal reaction force process for steering control of the operation steering unit 4 in response to the driver's steering manipulation of the steering wheel 3. In the embodiment, the normal control state is an example of the first state.

[0053] For example, the normal reaction force processing includes a cumulative rotation angle acquisition processing for calculating a steering angle θs which is a cumulative value obtained by referring to the rotation angle θa using the reaction force reference value θns as a reference value. The normal reaction force processing includes an end reaction force output processing for preventing the steering wheel 3 from rotating more than the limit rotation amount θ1 based on the steering angle θs.

[0054] More specifically, if Figure 3 As shown, in the end reaction force output process, the CPU 50a determines whether the absolute value of the steering angle θs is equal to or greater than the end threshold value θth (step 102). In step 102, the CPU 50a determines whether the steering angle θs is close to one of the right limit position 3a and the left limit position 3b. For example, the end threshold value θth is a value corresponding to the following position: slightly away from the right limit position 3a and the left limit position 3b toward the steering neutral position side, that is, the reaction force reference value θns side. That is, the end threshold value θth is a value slightly smaller than the absolute value of the right limit position 3a and the left limit position 3b.

[0055] Subsequently, when the absolute value of the steering angle θs is less than the end threshold value θth (step 102: No), the CPU 50a ends the processing and switches to another processing. On the other hand, when the absolute value of the steering angle θs is equal to or greater than the end threshold value θth (step 102: Yes), the CPU 50a calculates the end reaction force (step 104). In step 104, the CPU 50a calculates the end reaction force for notifying the driver that the steering angle θs is close to the right limit position 3a or the left limit position 3b. For example, the end reaction force is a value within a range that allows the driver's steering operation to be limited by experimental evaluation. The end reaction force is a component for quickly increasing the steering reaction force. The end reaction force calculated in this way is reflected in the steering reaction force that depends on the driver's steering operation, thereby limiting the driver's further steering to the right limit position 3a or the left limit position 3b that exceeds the end threshold value θth. Thereafter, the CPU 50a ends the processing and switches to another processing.

[0056] On the other hand, in the initial check process, in the case where the CPU 50a cannot read the reaction force reference value θns, the CPU 50a transitions to the normal control state after the control information setting state. In the initial check process, in the case where the reaction force reference value θns has not been internally set, the CPU 50a cannot read the reaction force reference value θns. The control information setting state is a state in which a control information setting process is performed for setting the reaction force reference value θns as a whole by a learning operation of rotating the steering wheel 3, i.e., the steering shaft 11 in the left and right directions. In the embodiment, the control information setting state is an example of the second state.

[0057] For example, the control information setting process includes a process of referring to the rotation angle θa. The CPU 50a includes a cumulative rotation angle acquisition process for calculating a temporary steering angle θsi, which is a cumulative value obtained by using the position of the rotation angle θa when the power is in the on state as a temporary reference value. The temporary steering angle θsi is a cumulative rotation angle, that is, an absolute rotation angle. The control information setting process includes a process of referring to the current iu1, iv1, iw1 and the steering torque Th. The control information setting process includes a learning process for internally setting the reaction force reference value θns based on the temporary steering angle θsi, the current iu1, iv1, iw1 and the steering torque Th.

[0058] More specifically, if Figure 4As shown, in the learning process, the CPU 50a rotates the steering wheel 3 in one of the right and left directions, that is, in the right direction as the first direction (step 202). In step 202, the CPU 50a calculates the control signal MSs for automatically rotating the steering wheel 3, that is, the steering shaft 11 in the right direction. In the learning process, the CPU 50a calculates the control signal MSs by performing feedback control so that the temporary steering angle θsi follows the target steering angle θs*. The target steering angle θs* is a value that is gradually changed and updated from the value of the temporary steering angle θsi at the start of the learning process to exceed the right limit position 3a.

[0059] Then, CPU 50a determines whether steering wheel 3 has reached rightward restricted position 3a (step 204). For example, in step 204, CPU 50a monitors currents iu1, iv1, iw1, steering torque Th, and angular velocity ωs as a change amount of temporary steering angle θsi.

[0060] The CPU 50a performs a process of determining whether the absolute value of the actual current value Ia obtained from the currents iu1, iv1, iw1 is equal to or greater than the current threshold value Iath. Determining whether the absolute value of the currents iu1, iv1, iw1 is equal to or greater than the current threshold value Iath corresponds to determining whether the load on the reaction force motor 13 has increased due to the steering shaft 11 having reached the rightward limit position 3a. For example, the current threshold value Iath is a value within a range evaluated by experiments so that the rotation of the steering shaft 11 is limited by the stop mechanism 11b, thereby limiting the rotation of the reaction force motor 13.

[0061] The CPU 50a performs a process of determining whether the absolute value of the steering torque Th is equal to or less than the torque threshold value Tth. Determining whether the absolute value of the steering torque Th is equal to or less than the torque threshold value Tth corresponds to determining whether the driver has made a steering intervention. For example, the torque threshold value Tth is a value within a range that can be determined by experimental evaluation that the driver has made a steering intervention.

[0062] The CPU 50a includes a process for determining whether the absolute value of the angular velocity ωs is equal to or less than the angular velocity threshold value ωth. Determining whether the absolute value of the angular velocity ωs is equal to or less than the angular velocity threshold value ωth corresponds to determining whether the steering shaft 11 has stopped because the steering shaft 11 has reached the rightward limit position 3a. For example, the angular velocity threshold value ωth is a value within a range evaluated by experiments so that the steering shaft 11 does not rotate.

[0063] In the event that the CPU 50a determines that the load on the reaction force motor 13 has increased, the driver has not made a steering intervention, and the steering shaft 11 has stopped, the CPU 50a includes processing to determine that the steering wheel 3 has reached the rightward limit position 3a.

[0064] Subsequently, in the case where the CPU 50a determines that the steering wheel 3 has not reached the right limit position 3a (step 204: No), the CPU 50a repeatedly executes the processing in steps 202 and 204. On the other hand, in the case where the CPU 50a determines that the steering wheel 3 has reached the right limit position 3a (step 204: Yes), the CPU 50a temporarily stores the right limit position θrl (step 206). In step 206, the CPU 50a temporarily stores the temporary steering steering angle θsi when it is determined that the steering wheel 3 has reached the right limit position 3a as the right limit position θrl.

[0065] Subsequently, the CPU 50a rotates the steering wheel 3 in the direction opposite to the right direction, that is, in the left direction as the second direction (step 208). In step 208, the CPU 50a calculates a control signal MSs for automatically rotating the steering wheel 3, that is, the steering shaft 11 in the left direction. For example, similar to the processing in step 202, the CPU 50a calculates the control signal MSs by performing feedback control so that the temporary steering angle θsi follows the target steering angle θs*. The target steering angle θs* is a value that is gradually changed and updated from the value of the temporary steering angle θsi when the steering wheel 3 has reached the right limit position 3a to exceed the left limit position 3b.

[0066] Subsequently, the CPU 50a determines whether the steering wheel 3 has reached the left limit position 3b (step 210). In step 210, similar to the processing in step 204, for example, the CPU 50a monitors the currents iu1, iv1, iw1, the steering torque Th, and the angular velocity ωs as the change amount of the temporary steering angle θsi.

[0067] Subsequently, in the case where the CPU 50a determines that the steering wheel 3 has not yet reached the left limit position 3b (step 210: No), the CPU 50a repeatedly executes the processing in steps 208 and 210. On the other hand, in the case where the CPU 50a determines that the steering wheel 3 has reached the left limit position 3b (step 210: Yes), the CPU 50a temporarily stores the left limit position θll (step 212). In step 212, the CPU 50a temporarily stores the temporary steering steering angle θsi when it is determined that the steering wheel 3 has reached the left limit position 3b as the left limit position θll.

[0068] Subsequently, the CPU 50a calculates the midpoint value θc (step 214). In step 214, the CPU 50a calculates a value corresponding to half of the sum of the right limit position θrl temporarily stored in step 206 and the left limit position θll temporarily stored in step 212 as the midpoint value θc. The midpoint value θc can be calculated by adding a value corresponding to half of the difference between the right limit position θrl and the left limit position θll to the left limit position θll. The absolute value of the difference between the midpoint value θc and the right limit position θrl and the absolute value of the difference between the midpoint value θc and the left limit position θll are equal to each other. The CPU 50a writes the midpoint value θc obtained in step 214 and sets it as the reaction force reference value θns, and ends the process to transition to another process. In the embodiment, the limit positions θrl, θll are examples of the first limit position and the second limit position.

[0069] Abnormal detection of the stop mechanism

[0070] When the power is on, the CPU 50a of the reaction force control unit 50 executes abnormality detection processing for detecting abnormality of the detent mechanism 11b in the vehicle steering system 2. The abnormality detection processing includes processing in modes depending on the normal control state and the control information setting state.

[0071] First abnormality detection process

[0072] For example, Figure 5 As shown, in the normal control state, the CPU 50a performs the first abnormality detection process. More specifically, the CPU 50a refers to the steering angle θs (step 302). The steering angle θs in step 302 is a first absolute rotation angle obtained using the reaction force reference value θns as a reference.

[0073] Subsequently, the CPU 50a determines whether the absolute value of the steering angle θs is equal to or less than the first threshold value Lth1 (step 304). In step 304, the CPU 50a determines whether the steering angle θs exceeds the limit rotation amount θ1 of the steering wheel 3. For example, the first threshold value Lth1 is set to a value in a range in which it can be determined that the steering angle θs exceeds the limit rotation amount θ1 of the steering wheel 3. The first threshold value Lth1 is set so that a lower limit value and an upper limit value are provided as shown in the following expression (1).

[0074] θ2≤Lth1≤Lca……(1)

[0075] Here, "θ2" is the absolute value of the angle corresponding to the right limit position 3a or the left limit position 3b, for example, the absolute value of the right limit position θr1 or the absolute value of the left limit position θll. That is, "θ2" is a value of half the limit rotation amount θ1 of the steering wheel 3 (θ1×(1 / 2)). In addition, "Lca" is the total length of the spiral cable 15d. That is, the first threshold value Lth1 is a value that is at least greater than the value θ2 of half the limit rotation amount θ1 of the steering wheel 3 and does not exceed the total length Lca of the spiral cable 15d.

[0076] In the embodiment, the first threshold value Lth1 is a value for which a mechanical tolerance θ3 and a detection margin θ4 are taken into consideration. The mechanical tolerance θ3 is a tolerance of the steering unit 4. The detection margin θ4 is a margin for suppressing erroneous determination when the CPU 50a executes step 304. That is, the first threshold value Lth1 is a value obtained by adding "θ2", "θ3", and "θ4".

[0077] In the case where the absolute value of the steering angle θs is less than the first threshold value Lth1, the CPU 50a determines that the abnormal condition is not satisfied. In this case, the CPU 50a does not detect the abnormality of the stopper mechanism 11b. On the other hand, in the case where the absolute value of the steering angle θs is equal to or greater than the first threshold value Lth1, the CPU 50a determines that the abnormal condition is satisfied. In this case, the CPU 50a detects the abnormality of the stopper mechanism 11b.

[0078] Subsequently, in the case where the absolute value of the steering angle θs is less than the first threshold value Lth1 (step 304: No), the CPU 50a determines that the abnormality of the stopper mechanism 11b has not been detected, and ends the processing to transition to another processing. On the other hand, in the case where the absolute value of the steering angle θs is equal to or greater than the first threshold value Lth1 (step 304: Yes), the CPU 50a determines that the abnormality of the stopper mechanism 11b has been detected, and sets the first fault state (step 306). In step 306, the CPU 50a calculates the control signal MSs by performing feedback control so that the steering angle θs follows the angle corresponding to the nearest end threshold value θth. For example, in the case where the steering wheel 3 is rotated in the right direction, the angle corresponding to the nearest end threshold value θth is the angle to the right limit position 3a side; and in the case where the steering wheel 3 is rotated in the left direction, the angle corresponding to the nearest end threshold value θth is the angle to the left limit position 3b.

[0079] In the first fault state, the CPU 50a includes a process of giving a notification indicating that it has been determined that an abnormality of the stop mechanism 11b has been detected to another control device equipped in the vehicle. For example, the other control device is a display device that gives information notifications by attracting the driver's visual senses and controls operations such as warnings. Examples of display devices include a head-up display (HUD), an instrument panel, a display of a navigation system, and a light-emitting diode (LED). In the case where the CPU 50a gives a notification indicating that it has been determined that an abnormality of the stop mechanism 11b has been detected, the CPU 50a, once the first fault state is set, will continue to give notifications to other control devices equipped in the vehicle when the power is in the on state, even when the power is temporarily turned off.

[0080] Second abnormality detection process

[0081] For example, Figure 6 As shown, in the control information setting state, the CPU 50a performs the second abnormality detection process. More specifically, the CPU 50a refers to the temporary steering angle θsi (step 402). The temporary steering angle θsi in step 402 is a second absolute rotation angle obtained without using the reaction force reference value θns as a reference.

[0082] Subsequently, the CPU 50a determines whether the absolute value of the temporary steering steering angle θsi is equal to or greater than the second threshold value Lth2 (step 404). In step 404, the CPU 50a determines whether the temporary steering steering angle θsi exceeds the limit rotation amount θ1 of the steering wheel 3. For example, the second threshold value Lth2 is set to a value in a range in which it can be determined that the temporary steering steering angle θsi exceeds the limit rotation amount θ1 of the steering wheel 3. The second threshold value Lth2 is set so that a lower limit value and an upper limit value are provided as shown in the following expressions (2) and (3).

[0083] θ1≤Lth2……(2)

[0084] Lth2+(Lth1+θ5)≤Lca……(3)

[0085] Here, "θ1", "Lca", and "Lth1" are the same as those in expression (1). In addition, "θ5" is an adjustment amount related to the configuration of the locking mechanism 16. For example, the adjustment amount θ5 is an amount by which the steering shaft 11 moves in one of the right and left directions when the locking mechanism 16 becomes a locked state and is thus assembled in the gear portion of the steering shaft 11. That is, the adjustment amount θ5 is a value corresponding to one tooth of the gear portion of the steering shaft 11.

[0086] From expressions (2) and (3), the following expression (4) is obtained.

[0087] θ1≤Lth2≤Lca-(Lth1+θ5)……(4)

[0088] That is, the second threshold value Lth2 is a value that is at least equal to or greater than the limited rotation amount θ1 of the steering wheel 3 and does not exceed the total length Lca of the spiral cable 15 d .

[0089] In the embodiment, the second threshold value Lth2 is a value for which the mechanical tolerance θ3 and the detection margin θ6 are taken into consideration. The detection margin θ6 is a margin for suppressing erroneous determination when the CPU 50a executes step 404. For example, the detection margin θ6 is a value smaller than the detection margin θ4 in a normal control state. That is, the second threshold value Lth2 is equal to or greater than a value obtained by adding "θ1", "θ3" and "θ6".

[0090] In the case where the absolute value of the temporary steering steering angle θsi is less than the second threshold value Lth2, the CPU 50a determines that the abnormal condition is not satisfied. In this case, the CPU 50a does not detect the abnormality of the detent mechanism 11b. On the other hand, in the case where the absolute value of the temporary steering steering angle θsi is equal to or greater than the second threshold value Lth2, the CPU 50a determines that the abnormal condition is satisfied. In this case, the CPU 50a detects the abnormality of the detent mechanism 11b.

[0091] Subsequently, in the case where the absolute value of the temporary steering steering angle θsi is less than the second threshold value Lth2 (step 404: No), the CPU 50a determines that the abnormality of the stopper mechanism 11b has not been detected, and ends the processing to transition to another processing. On the other hand, in the case where the absolute value of the temporary steering steering angle θsi is equal to or greater than the second threshold value Lth2 (step 404: Yes), the CPU 50a determines that the abnormality of the stopper mechanism 11b has been detected, and sets the second fault state (step 406). In step 406, the CPU 50a calculates the control signal MSs by performing feedback control so that the temporary steering steering angle θsi is maintained at the current angle.

[0092] In the second fault state, similar to the first fault state, the CPU 50a performs processing for giving a notification indicating that the abnormality of the stopper mechanism 11b has been determined to be detected to another control device equipped in the vehicle. That is, in the case where the CPU 50a gives a notification indicating that the abnormality of the stopper mechanism 11b has been determined to be detected, the CPU 50a, after once setting the second fault state, continues to give the notification to the other control device equipped in the vehicle when the power is in the on state, even when the power is temporarily turned off.

[0093] Operation of Embodiments

[0094] Figure 5 The first abnormality determination processing in includes a process of determining whether the absolute value of the steering angle θs is equal to or greater than a first threshold value Lth1 (step 304).

[0095] For example, Figure 7 As shown, in the normal control state, when the steering wheel 3 rotates to the right relative to the reaction force reference value θns and the steering angle θs is equal to or greater than the first threshold value Lth1, the probability that the steering wheel 3 rotates beyond the right limit position 3a is high. This is because, as shown in expression (1), the first threshold value Lth1 is equal to or greater than "θ2" and equal to or less than "Lca".

[0096] Assuming that the steering wheel 3 rotates to the right more than half of the limit rotation amount θ1 in the normal control state, the lower limit value of the first threshold value Lth1 is set to "θ2". That is, the first threshold value Lth1 is set assuming that the steering wheel 3 rotates to the right more than the limit position 3a or the limit position 3b in the normal control state.

[0097] Assuming that the steering wheel 3 rotates to the right direction without exceeding the total length Lca of the spiral cable 15d in the normal control state, the upper limit value of the first threshold value Lth1 is set to "Lca". That is, the first threshold value Lth1 is set assuming that the steering wheel 3 rotates to the left and right directions without exceeding the total length Lca of the spiral cable 15d in the normal control state.

[0098] Therefore, by executing the processing in step 304, the CPU 50a can detect using software that the steering angle θs exceeds the limit rotation amount θ1 of the steering wheel 3. The CPU 50a can detect using software that the steering angle θs exceeds the limit rotation amount θ1 of the steering wheel 3 in a range where the total length Lca of the spiral cable 15d is not exceeded.

[0099] Figure 6 The second abnormality determination process in includes a process for determining whether the absolute value of the temporary steering angle θsi is equal to or greater than the second threshold value Lth2 (step 404). Figure 7 As shown, in the control information setting state, when the steering wheel 3 is rotated in the right direction by the learning operation and the temporary steering angle θsi is equal to or greater than the second threshold value Lth2, the probability that the steering wheel 3 is rotated beyond the right limit position 3a is high. This is because, as shown in Expression (4), the second threshold value Lth2 is equal to or greater than "θ1" and equal to or less than the value obtained by subtracting "Lth1" and "θ5" from "Lca".

[0100] Assuming the first case that the steering wheel 3 has been rotated to the left limit position 3b in the initial state, the lower limit value of the second threshold value Lth2 is set to "θ1". That is, the second threshold value Lth2 is set assuming the first case that the steering wheel 3 has been rotated to the limit position on the opposite side of the direction in which the steering wheel 3 is rotated by the learning operation in the initial state.

[0101] Furthermore, assuming the second case that the initial state of the steering wheel 3 is a state corresponding to the first threshold value Lth1, the upper limit value of the second threshold value Lth2 is set to a value obtained by subtracting "Lth1" and "θ5" from "Lca". Assuming the case that the steering wheel 3 is rotated in the right direction from the second case without exceeding the total length Lca of the spiral cable 15d, the upper limit value of the second threshold value Lth2 is set to a value obtained by subtracting "Lth1" and "θ5" from "Lca". That is, the second threshold value Lth2 is set assuming the second case that the steering wheel 3 has been rotated to the vicinity of the limit position on one side of the direction in which the steering wheel 3 is rotated by the learning operation in the initial state. Even in the case of assuming the first case and the second case, the second threshold value Lth2 is set assuming the case that the steering wheel 3 is rotated in the left and right directions by the learning operation without exceeding the total length Lca of the spiral cable 15d.

[0102] Therefore, by executing the processing in step 404, the CPU 50a can detect using software that the temporary steering steering angle θsi exceeds the limit rotation amount θ1 of the steering wheel 3. The CPU 50a can detect using software that the temporary steering steering angle θsi exceeds the limit rotation amount θ1 of the steering wheel 3 in a range where the total length Lca of the spiral cable 15d is not exceeded.

[0103] Effects of implementation methods

[0104] (1-1) The CPU 50a of the reaction force control unit 50 executes Figure 5 The first abnormality determination process in Figure 6 The second abnormality determination process in is used to detect the abnormality of the stopper mechanism 11b. Therefore, in the vehicle steering system 2, even in the case where the stopper mechanism 11b becomes unable to mechanically limit the rotation range of the steering shaft 11, early detection is possible. Therefore, even in the case where such a problem that the steering shaft 11 continues to rotate without restriction occurs, such a problem can be dealt with at an early stage.

[0105] (1-2) The CPU 50a executes processing in which the satisfaction requirement of the abnormal condition is different depending on whether the state is the normal control state or the control information setting state. Therefore, in the vehicle steering system 2 in which the normal control state and the control information setting state can be set, it is possible to appropriately determine that the steering angle θs and the temporary steering angle θsi exceed the limit rotation amount θ1 of the steering wheel 3 regardless of the state. Therefore, the abnormality of the stopper mechanism 11b can be detected at an early stage regardless of whether the reaction force reference value θns has been set internally.

[0106] (1-3) In the first abnormality determination process, when the magnitude of the steering steering angle θs is determined in the normal control state, the first threshold value Lth1 is used, and thus, a process of appropriately determining the abnormality of the stopper mechanism 11b is included. On the other hand, in the second abnormality determination process, when the magnitude of the temporary steering steering angle θsi is determined in the control information setting state, the second threshold value Lth2 different from the first threshold value Lth1 is used, and thus, the abnormality of the stopper mechanism 11b can be appropriately determined. Therefore, determination can be performed according to the normal control state and the control information setting state.

[0107] (1-4) For example, as an assumed initial state of the steering wheel 3 in the control information setting state, a case is possible where the steering wheel 3 rotates until just before transitioning to a state corresponding to the first threshold value Lth1. In this case, in a case where the lock mechanism 16 is in the locked state, it is possible that the steering wheel 3 rotates beyond the first threshold value Lth1 also due to the configuration of the lock mechanism 16. However, the upper limit value of the second threshold value Lth2 is a value for which the adjustment amount θ5 is taken into consideration. Therefore, an abnormality of the stopper mechanism 11b can be appropriately detected.

[0108] (1-5) Figure 7 As shown, the first threshold value Lth1 is a value for which the mechanical tolerance θ3 and the detection margin θ4 are taken into consideration. Figure 7 As shown, the second threshold value Lth2 is a value for which the mechanical tolerance θ3 and the detection margin θ6 are taken into consideration. Therefore, it is possible to appropriately suppress erroneous detection of abnormality of the stopper mechanism 11b.

[0109] (1-6) Figure 7 As shown, the first threshold value Lth1 is a value in a range in which the total length Lca of the spiral cable 15d is not exceeded. Figure 7As shown, the second threshold value Lth2 is a value in a range in which the total length Lca of the spiral cable 15d is not exceeded. In particular, the second threshold value Lth2 is a value that is smaller than the total length Lca of the spiral cable 15d by at least a value obtained by adding "Lth1" and "θ5". Therefore, even in a case where the stopper mechanism 11b becomes unable to mechanically limit the rotation range of the steering shaft 11, it is possible to suppress excessive force from being applied to the spiral cable 15d. Therefore, it is also possible to ensure protection of the spiral cable 15d.

[0110] (1-7) The CPU 50a executes a learning process for internally setting the reaction force reference value θns as a process executed in the control information setting state. Therefore, even during the learning operation, an abnormality of the stopper mechanism 11b can be appropriately detected.

[0111] Other Implementations

[0112] The above embodiments may be modified as follows. Furthermore, the following other embodiments may be combined with each other within a range in which there is no technical inconsistency.

[0113] The lower limit value of the first threshold value Lth1 may be a value for which "θ3" or "θ4" is taken into consideration. For example, the lower limit value of the first threshold value Lth1 may be a value obtained by adding "θ2", "θ3" and "θ4". In addition, the upper limit value of the first threshold value Lth1 may be a value for which "θ5" is taken into consideration. In addition, depending on the size of the total length Lca of the spiral cable 15d, the upper limit value of the first threshold value Lth1 may be a value of half the total length Lca, or a value less than half the total length Lca.

[0114] The lower limit value of the second threshold value Lth2 may be a value for which "θ3" or "θ6" is considered. For example, the upper limit value of the second threshold value Lth2 may be a value obtained by adding "θ1", "θ3", and "θ6". In addition, the upper limit value of the second threshold value Lth2 only needs to be a value for which at least "Lth1" is considered, and may be a value for which "θ5" is not considered.

[0115] The mechanical tolerance θ3 is a value that can be changed as appropriate according to the configuration of the steering unit 4 .

[0116] The same value may be employed as the detection margin θ4 and the detection margin θ6.

[0117] The adjustment amount θ5 is a value that can be changed as appropriate according to the configuration of the lock mechanism 16 .

[0118] In the first fault state, the CPU 50a may calculate the control signal MSs by performing feedback control so as to maintain the steering angle θs at the current angle.

[0119] In the second fault state, the CPU 50a may switch the locking mechanism 16 to the locked state.

[0120] The CPU 50a may execute only one of the first abnormality determination process and the second abnormality determination process. That is, a configuration may be adopted in which the abnormality of the stopper mechanism 11b is detected in only one of the normal control state and the control information setting state.

[0121] The second abnormality determination process can be applied as a process executed in a normal control state. In the control information setting state, when the steering wheel 3 is approximately in the steering neutral position as the assumed initial state of the steering wheel 3, the first abnormality determination process can be applied as a process executed in the control information setting state.

[0122] The method for internally setting the reaction force reference value θns is not limited to the method in which the learning operation is performed, and may be changed as appropriate, for example, to a method in which the setting is performed manually by a worker.

[0123] The learning process may be a process of first rotating the steering wheel 3 in the left direction, and then rotating the steering wheel 3 in the right direction. In this case, Figure 4 The processing in may be configured such that the processing in steps 208 , 210 , and 212 may be performed before the processing in steps 202 , 204 , and 206 .

[0124] The learning process only needs to include a process of temporarily storing one of the respective limit positions θrl, θll. That is, the process regarding the learning operation may exclude a process of temporarily storing the other of the respective limit positions θrl, θll. For example, in the case of a process including temporarily storing the right limit position θrl, the CPU 50a may calculate a value obtained by subtracting a value θ2 which is half of the limit rotation amount θ1 from the right limit position θrl as the midpoint value θc.

[0125] The learning process may include a process of determining the validity of the midpoint value θc.

[0126] In the learning process, the processes in step 204 and step 210 only need to be processes of at least determining whether the absolute value of the actual current value Ia is equal to or greater than the current threshold value Iath.

[0127] In the learning process, in addition to the above embodiments, other parameters may be considered in the processes of step 204 and step 210. Examples of other parameters may include the amount of change in the actual current value Ia, the amount of change in the angular velocity ωs, and the time since the steering wheel 3 started rotating.

[0128] The CPU 50 a may execute control for executing switching between the locked state and the unlocked state of the lock mechanism 16 .

[0129] The displacement amount of the steering wheel 3 is not limited to the amount calculated based on the cumulative processing of the rotation angle θa. For example, the detection value of the steering angle sensor that directly detects the rotation angle of the steering shaft 11 may be used. For example, the steering angle sensor may be provided in the steering shaft 11 between the steering wheel 3 and the torque sensor 41. In other embodiments of the description, the steering angle sensor is an example of an angle sensor.

[0130] The steering actuator 12 does not need to include the steering-side speed reduction mechanism 14 .

[0131] The reaction force motor 13 is not limited to a three-phase brushless motor. For example, a DC motor with a brush may be used. The other embodiments described above may be similarly applied to the steering motor 32.

[0132] The steering unit 6 transmits the rotation of the steering motor 32 to the conversion mechanism 34 through the transmission mechanism 33, but is not limited thereto, and for example, the steering unit 6 may be configured to transmit the rotation of the steering motor 32 to the conversion mechanism 34 through a gear mechanism. In addition, the steering unit 6 may be configured so that the steering motor 32 directly rotates the conversion mechanism 34. In addition, the steering unit 6 may be configured to include a second rack and pinion mechanism, and the steering unit 6 may be configured so that the second rack and pinion mechanism converts the rotation of the steering motor 32 into the reciprocating motion of the rack shaft 22.

[0133] The steering unit 6 is not limited to the configuration in which the steering wheel 5 on the right and the steering wheel 5 on the left are interlocked. In other words, the steering wheel 5 on the right and the steering wheel 5 on the left can be independently controlled.

[0134] In the above embodiment, the vehicle steering system 2 has a linkless structure in which the steering control unit 4 and the steering unit 6 are always mechanically separated, but is not limited to this. The vehicle steering system 2 may have a structure in which the steering control unit 4 and the steering unit 6 may be mechanically separated by a clutch.

Claims

1. A steering control device (1), the steering control device (1) being applied to a vehicle steering system, the vehicle steering system having a structure in which a power transmission path between a steering unit (4) and a steering unit (6) is cut off, the steering unit (4) being configured to be steered by a steering wheel (3) of the vehicle, the steering unit (6) being configured to be operated to steer a steering wheel of the vehicle, the steering unit (4) comprising a steering shaft (11), a reaction force motor (13), a stopper mechanism (11b), and an angle sensor (42), the steering shaft (11) being connected to the steering wheel (3), the reaction force motor (13) being configured to apply a motor torque to the steering shaft (11) to apply a steering reaction force to the steering wheel (3), the stopper mechanism (11b) being configured to limit the rotation of the steering shaft (11) in the left-right direction within a limited rotation amount, and the angle sensor (42) being configured to detect the rotation angle of the steering shaft (11), The steering control device (1) is characterized in that it includes a processor (50a) for controlling the steering unit (4), wherein the steering unit (4) uses the reaction force motor (13) as a driving source. The processor (50a) is configured to execute: a cumulative rotation angle acquisition process for acquiring a cumulative rotation angle based on a detection result of the angle sensor (42), the cumulative rotation angle being a cumulative value of the rotation angle of the steering shaft (11); and An abnormality determination process is performed to determine whether an abnormality condition is satisfied based on the accumulated rotation angle, the abnormality condition being a condition for detecting an abnormality of the stopper mechanism (11b), wherein: The abnormality determination process includes: when the processor (50a) can determine that the cumulative rotation angle exceeds the limit rotation amount, determining that the abnormal condition is satisfied.

2. The steering control device (1) according to claim 1, characterized in that: The cumulative rotation angle acquisition process includes: a process of acquiring a first absolute rotation angle in a first state in which a reference value indicating a neutral position of the steering wheel (3) has been internally set, the first absolute rotation angle being the accumulated rotation angle relative to the reference value, and a process of acquiring a second absolute rotation angle in a second state in which the reference value is not internally set, the second absolute rotation angle being the accumulated rotation angle in which the reference value is not used as a reference; and The abnormality determination process includes: in the first state, determining a first abnormality determination process that satisfies the abnormality condition based on the first absolute rotation angle, and In the second state, a second abnormality determination process is determined to satisfy the abnormality condition based on the second absolute rotation angle.

3. The steering control device (1) according to claim 2, characterized in that: The first abnormality determination processing is a processing for determining that the abnormal condition is satisfied when the processor (50a) is able to determine that the magnitude of the first absolute rotation angle is equal to or greater than a first threshold value, the first threshold value being a value equal to or greater than half of the limited rotation amount; as well as The second abnormality determination processing is a processing for determining that the abnormal condition is satisfied when the processor (50a) can determine that the magnitude of the second absolute rotation angle is equal to or greater than a second threshold value, the second threshold value being a value equal to or greater than the limited rotation amount.

4. The steering control device (1) according to claim 3, characterized in that: The steering unit (4) comprises a locking mechanism (16), wherein the locking mechanism (16) is configured to mechanically lock the rotation of the steering shaft (11); The second state is a state to which the steering control device (1) changes from a state in which the locking mechanism (16) locks the rotation of the steering shaft (11); The first state comprises a state to which the steering control device (1) transitions after the second state; and The second threshold value is a value for which the first threshold value and an adjustment amount related to at least the configuration of the locking mechanism (16) are taken into account.

5. The steering control device (1) according to any one of claims 2 to 4, characterized in that: The reference value is a value obtained through a learning operation in which the steering shaft (11) moves to a limiting position in a first direction and a limiting position in a second direction; The processor (50a) is configured to execute a learning process in the second state, the learning process being a process for internally setting the reference value through the learning operation; as well as The learning process includes: During the learning operation, a process of acquiring a first limit position which is an angle corresponding to the position of the steering shaft (11) at the limit position in the first direction and a second limit position which is an angle corresponding to the position of the steering shaft (11) at the limit position in the second direction, and The process of setting the reference value based on the limit position acquired for each direction.

6. A steering control method, the steering control method being applied to a vehicle steering system, the vehicle steering system having a structure in which a power transmission path between a steering unit (4) and a steering unit (6) is cut off, the steering unit (4) being configured to be steered by a steering wheel (3) of the vehicle, the steering unit (6) being configured to be operated to steer a steering wheel of the vehicle, The steering control method is characterized in that it includes controlling the steering unit (4) by a processor (50a), the steering unit (4) using a reaction force motor (13) as a driving source, the reaction force motor (13) being configured to apply a motor torque to a steering shaft (11) connected to the steering wheel (3) to apply a steering reaction force to the steering wheel (3), wherein: The controlling of the steering control unit (4) by the processor (50a) comprises: acquiring a cumulative rotation angle based on a detection result of an angle sensor (42), the angle sensor (42) being configured to detect the rotation angle of the steering shaft (11), the cumulative rotation angle being a cumulative value of the rotation angle of the steering shaft (11); and determining whether an abnormal condition is satisfied based on the accumulated rotation angle, the abnormal condition being a condition for detecting an abnormality of a stopper mechanism (11b), the stopper mechanism (11b) being configured to limit the rotation of the steering shaft (11) in the left-right direction within a limited rotation amount, The determining whether the abnormal condition is satisfied includes: when the processor (50a) is able to determine that the accumulated rotation angle exceeds the limit rotation amount, determining that the abnormal condition is satisfied.

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