Steering control unit

Abstract

A steering control device (50) includes a base axial force calculator (81), a limiting axial force calculator (82), and a final axial force calculator (83). The limiting axial force calculator (82) includes a steering angle holder (91), a reference angle calculator (93), a final difference calculator (94), and an axial force calculator (95). The steering angle holder (91) is configured to maintain the steering angle at the time of the limited steering operation when the steering operation of the steering wheel (16) is limited. The reference angle calculator (93) is configured to calculate a reference angle. The final difference calculator (94) is configured to calculate the final difference as the final difference between the reference angle and the current steering angle. The axial force calculator (95) is configured to calculate the limiting axial force based on the value of the final difference.

Description

Technical Field

[0001] This invention relates to a steering control device. Background Technology

[0002] A known steer-by-wire system is described, in which the power transmission path between the steering wheel and the turning wheels is interrupted. The system includes a reaction force motor, a steering motor, and a control unit. The reaction force motor generates a steering reaction force applied to the steering shaft. The steering motor generates a turning force to turn the turning wheels. When the vehicle is in motion, the control unit generates the steering reaction force by controlling the reaction force motor and turns the turning wheels by controlling the steering motor.

[0003] For example, the steering control device disclosed in Japanese Unexamined Patent Application Publication No. 2014-133534 (JP 2014-133534 A) calculates the conventional reaction force based on the steering wheel angle, the turning wheel angle, and the vehicle speed. The steering control device also calculates the end contact reaction force based on the steering angle and the turning angle. The end contact reaction force is the reaction force used to provide the driver with the end contact feel of the steering mechanism. The steering control device calculates the final steering reaction force based on the conventional reaction force and the end contact reaction force. The steering control device controls the power supply to the reaction force motor, causing the reaction force motor to generate the final steering reaction force.

[0004] Vibration may occur because the direction of the regular reaction force, which increases with the absolute value of the steering angle or turning angle, is opposite to the direction of the end contact reaction force, which increases with the increase of the difference between the absolute value of the steering angle and the upper limit threshold. Therefore, the steering control device disclosed in JP 2014-133534 A corrects for at least one of the regular reaction force and the end contact reaction force, such that when the direction of the regular reaction force is opposite to the direction of the end contact reaction force, the absolute value of the regular reaction force is relatively reduced. Therefore, even when the direction of the regular reaction force is opposite to the direction of the end contact reaction force, vibration can be suppressed. Summary of the Invention

[0005] The steering control device disclosed in JP 2014-133534 A calculates the regular reaction force and the end contact reaction force separately, and performs a process to correct at least one of the regular reaction force and the end contact reaction force based on the direction of the calculated reaction force. Thus, the calculation of multiple reaction forces and the execution of the process of adjusting multiple reaction forces act as a factor that hinders the reduction of the computational load of the steering control device. Therefore, there is a need to reduce the computational load in steering control devices based on related technologies including the steering control device disclosed in JP 2014-133534 A.

[0006] One aspect of the present invention provides a steering control device. The steering control device controls a reaction force motor configured to generate a steering reaction force applied to a steering wheel based on a command value calculated according to a steering state, wherein the power transmission path of the steering wheel to and from the steering axle that causes the steering wheels to turn is interrupted. The steering control device includes: a basic axial force calculator configured to calculate a basic axial force including axial forces reflecting forces acting on the steering axle via at least the steering wheels when the steering wheel is operated within a predetermined operating range; a limiting axial force calculator configured to calculate a limiting axial force, which is an axial force used to virtually limit the operation of the steering wheel; and a final axial force calculator configured to calculate a final axial force based on the basic axial force and the limiting axial force, which is the final axial force to be reflected in the command value. The limiting axial force calculator includes a steering angle retainer, a reference angle calculator, a final difference calculator, and an axial force calculator. The steering angle retainer is configured to maintain a steering angle at which the steering wheels are limited during turning operations when turning operations are restricted. The reference angle calculator is configured to calculate the reference angle when the turning operation of the steering wheel is restricted by executing a limiting process that restricts the steering angle held by the steering angle retainer to a virtual end angle. The reference angle calculator is also configured to calculate the reference angle when the turning operation of the steering wheel is unrestricted by executing a limiting process that restricts the current steering angle to a virtual end angle. The virtual end angle corresponds to the restricted position of the virtual operating range of the steering wheel. The final difference calculator is configured to calculate the final difference, which is the final difference between the reference angle and the current steering angle. The axial force calculator is configured to calculate the limiting axial force based on the value of the final difference.

[0007] This configuration calculates a limiting axial force corresponding to the difference between the current steering angle and the current steering angle when the turning wheel's turning operation is restricted. By reflecting this limiting axial force in the final axial force or command value, a driving force is applied to the vehicle's steering mechanism to virtually restrict steering wheel operation. Therefore, the driver can identify when the turning wheel's turning operation is restricted through the response from the steering wheel.

[0008] When the turning wheel is not restricted and the steering wheel is operated beyond the virtual end angle, a limiting axial force corresponding to the difference between the current steering angle and the virtual end angle is calculated. This limiting axial force is reflected in the final axial force or command value, and a driving force used to virtually limit steering wheel operation is applied to the vehicle's steering mechanism. Therefore, the driver can identify situations where the steering wheel has been operated beyond the virtual operating range's limit based on the response from the steering wheel.

[0009] Here, it can be envisioned that when the turning operation of the steering wheel is restricted, the limiting axial force for restricting additional steering wheel operations and the limiting axial force for restricting steering wheel operations exceeding the virtual end angle are calculated separately. In this case, for example, from the viewpoint of providing the driver with appropriate steering feel, it is necessary to perform a process of adjusting the two limiting axial forces.

[0010] In this configuration, one of the limiting axial forces—one for restricting additional steering wheel operations when steering wheel operations are restricted, and the other for restricting steering wheel operations exceeding the virtual end angle—is calculated based on the difference between a reference angle calculated according to whether steering wheel operations are restricted and the current steering angle. That is, a portion of the calculation for both the limiting axial force for restricting additional steering wheel operations and the limiting axial force for restricting steering wheel operations exceeding the virtual end angle is shared when steering wheel operations are restricted. Therefore, there is no need to perform the process of adjusting the two limiting axial forces. Thus, the computational load can be reduced when calculating the two limiting axial forces separately.

[0011] In the steering control unit, the final difference calculator can be configured to correct the calculated final difference value to a smaller value when the turning action of the turning wheels is restricted. When the turning wheels are about to turn under restricted turning action, the reaction force increases slowly with the elastic deformation of the tires. With this configuration, the steering reaction force can be increased more slowly by correcting the calculated final difference value to a smaller value. Therefore, a steering reaction force that more closely resembles the actual steering reaction force in the case where the turning action of the turning wheels is restricted can be applied to the steering wheel.

[0012] In the steering control device, the final difference calculator can be configured to use the larger of the final difference calculated based on the premise that the turning operation of the turning wheel is restricted and the final difference calculated based on the premise that the rotation position of the steering wheel has reached the limit position of the virtual operating range when the turning operation of the turning wheel is restricted and the rotation position of the steering wheel has reached the limit position of the virtual operating range.

[0013] With this configuration, a steering reaction force corresponding to the final difference can be applied to the steering wheel. This final difference has the larger of two values: a final difference calculated based on the premise that the turning operation of the turning wheel is restricted, and a final difference calculated based on the premise that the rotation position of the steering wheel reaches the restricted position of the virtual operating range.

[0014] The steering control device may further include: a gain calculator configured to calculate a damping gain for limiting the axial force based on the value of the final difference calculated by the final difference calculator; and a multiplier configured to calculate the damping axial force to be reflected in the limiting axial force by multiplying the gain calculated by the gain calculator by the steering angular velocity.

[0015] As the gradient of the limiting axial force relative to the final difference increases, the value of the limiting axial force may oscillate relative to the value of the final difference. With this configuration, the value of the limiting axial force can be stabilized relative to the final difference by reflecting the damping axial force in the limiting axial force.

[0016] The steering control unit may further include a difference calculator configured to calculate the difference between the turning angle of the turning wheel when the turning operation of the turning wheel is restricted and the current turning angle. A reference angle calculator may be configured to correct the steering angle held by the steering angle holder based on the value of the difference calculated by the difference calculator when the turning operation of the turning wheel is restricted, and to calculate a reference angle by performing a limiting process on the corrected steering angle.

[0017] Even when the turning operation of the steering wheels is restricted, the steering wheels may still turn slightly. With this configuration, the steering angle held by the steering angle retainer is corrected based on the amount of rotation of the shaft interlocked with the turning operation of the steering wheels. The reference angle is calculated based on the corrected steering angle. Therefore, even when the turning wheels are turned with restricted turning operation, a more appropriate steering reaction force can be applied to the steering wheel.

[0018] The computational load can be reduced by using the steering control device according to the present invention. Attached Figure Description

[0019] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals denote the same elements, and in the drawings:

[0020] Figure 1 This is a diagram showing the configuration of a steer-by-wire system equipped with a steering control device according to an embodiment;

[0021] Figure 2 This is a block diagram of the control device according to the implementation method;

[0022] Figure 3 This is a block diagram of the steering reaction force command value calculator according to the implementation method;

[0023] Figure 4 This is a control block diagram of the axial force limiting calculator according to the implementation method;

[0024] Figure 5 It is a graph showing the relationship between the final difference and the pre-limited axial force according to the embodiment; and

[0025] Figure 6 It is a graph showing the relationship between the final difference and the gain according to the implementation method. Detailed Implementation

[0026] The steering control device according to an embodiment will be described below. For example... Figure 1 As shown, the vehicle's steering system 10 includes a steering shaft 12 connected to a steering wheel 11. The steering system 10 includes a steering shaft 12 along the vehicle's width direction (…). Figure 1 A turning axle 14 extends in the left-right direction. Left and right turning wheels 16 are connected to both ends of the turning axle 14 via tie rods 15 and 15. When the turning axle 14 moves linearly, the turning angle θ of the turning wheels 16... w Changes. Steering shaft 12 and turning shaft 14 constitute the vehicle's steering mechanism.

[0027] The steering system 10 includes a reaction force motor 31, a reduction gear mechanism 32, a rotation angle sensor 33, and a torque sensor 34 as a configuration for generating steering reaction force. The steering reaction force is a force acting in the opposite direction to the direction of operation of the steering wheel 11 operated by the driver. By applying a steering reaction force to the steering wheel 11, an appropriate responsiveness can be provided to the driver.

[0028] The reaction force motor 31 is the source of the steering reaction force. For example, a three-phase brushless motor is used as the reaction force motor 31. The rotation shaft of the reaction force motor 31 is connected to the steering shaft 12 via a reduction gear mechanism 32. The torque of the reaction force motor 31 is applied to the steering shaft 12 as the steering reaction force. The torque of the reaction force motor 31 is the driving force applied to the steering shaft 12.

[0029] A rotation angle sensor 33 is installed in the reaction force motor 31. The rotation angle sensor 33 detects the rotation angle θ of the reaction force motor 31. a The rotation angle θ of the reaction force motor 31 a Used to calculate steering angle θ s The reaction force motor 31 and the steering shaft 12 are interlocked via a reduction gear mechanism 32. Therefore, the rotation angle θ of the reaction force motor 31... a The rotation angle relative to the steering axis 12, i.e., the steering angle θ which is the rotation angle of the steering wheel 11. s This is relevant. Therefore, it can be based on the rotation angle θ of the reaction force motor 31. a To calculate the steering angle θ s .

[0030] Torque sensor 34 detects steering torque T h Steering torque T h The torque is applied to the steering shaft 12 by rotating the steering wheel 11. The torque sensor 34 detects the steering torque T applied to the steering shaft 12 based on the amount of torsion of the torsion bar located in the middle of the steering shaft 12. hThe torque sensor 34 is disposed in the portion of the steering shaft 12 between the reduction gear mechanism 32 and the steering wheel 11.

[0031] The steering system 10 includes a steering motor 41, a reduction gear mechanism 42, and a rotation angle sensor 43 as a configuration to generate a steering force, which is the power used to turn the steering wheel 16. The steering motor 41 is the source of the steering force. For example, a three-phase brushless motor is used as the steering motor 41. The rotation shaft of the steering motor 41 is connected to a pinion shaft 44 via the reduction gear mechanism 42. The pinion teeth 44a of the pinion shaft 44 mesh with the rack teeth 14b of the steering shaft 14. The torque of the steering motor 41 is applied to the steering shaft 14 as a steering force via the pinion shaft 44. The torque of the steering motor 41 is the driving force applied to the steering shaft 14. As the steering motor 41 rotates, the steering shaft 14 moves along the vehicle width direction ( Figure 1 Move in the left and right directions.

[0032] A rotation angle sensor 43 is installed in the turning motor 41. The rotation angle sensor 43 detects the rotation angle θ of the turning motor 41. b The steering system 10 includes a pinion shaft 13. The pinion shaft 13 is configured to span a turning shaft 14. The pinion teeth 13a of the pinion shaft 13 mesh with the rack teeth 14a of the turning shaft 14. The reason for providing the pinion shaft 13 is that the turning shaft 14 and the pinion shaft 44 are thus supported together in a housing (not shown). That is, by means of a support mechanism (not shown) provided in the steering system 10, the turning shaft 14 is supported so as to be able to move axially and is pressed against the pinion shafts 13 and 44. Therefore, the turning shaft 14 is supported in the housing. Another support mechanism can be provided to support the turning shaft 14 in the housing without using the pinion shaft 13.

[0033] The steering system 10 includes a control unit 50. The control unit 50 may be configured as processing circuitry, which includes: (1) one or more processors operating according to a computer program (software); (2) one or more dedicated hardware circuits, such as application-specific integrated circuits (ASICs) performing at least some of the various processes; or (3) combinations thereof. The processor includes a central processing unit (CPU). The processor includes memories such as RAM and ROM. The memories store program code or commands configured to cause the CPU to perform processes. Memory, i.e., non-transitory computer-readable media, includes all available media accessible by a general-purpose or special-purpose computer. The control unit 50 corresponds to a steering control unit.

[0034] The control unit 50 controls the reaction force motor 31 and the steering motor 41 based on detection results from various sensors installed in the vehicle. In addition to the rotation angle sensor 33, torque sensor 34, and rotation angle sensor 43, examples of sensors include a vehicle speed sensor 501. The vehicle speed sensor 501 detects the vehicle speed V.

[0035] Control device 50 performs reaction force control, thereby generating a steering torque T by controlling reaction force motor 31. h The corresponding steering reaction force. Control device 50 is based on steering torque T. h The target steering reaction force is calculated based on the vehicle speed V, and a steering reaction force command value is calculated based on the calculated target steering reaction force. The control device 50 supplies the current required to generate the steering reaction force corresponding to the steering reaction force command value to the reaction force motor 31.

[0036] Control device 50 performs turning control, causing the turning wheel 16 to turn according to the steering state by controlling the turning motor 41. Control device 50 bases its control on the rotation angle θ of the turning motor 41 detected by the rotation angle sensor 43. b To calculate the pinion angle θ, which is the actual rotation angle of the pinion shaft 44. p pinion angle θ p It reflects the turning angle θ of the turning wheel 16. w The value of the control device 50 is based on the rotation angle θ of the reaction force motor 31 detected by the rotation angle sensor 33. a To calculate the steering angle θ s And based on the calculated steering angle θ s To calculate the pinion angle θ p The target value is the target pinion angle. Control device 50 calculates the target pinion angle and the actual pinion angle θ. p The difference between them is eliminated by controlling the power supply to the turning motor 41.

[0037] Configuration of control device

[0038] The configuration of the control device 50 will be described below. For example... Figure 2 As shown, the control device 50 includes a reaction force controller 50a that performs reaction force control and a turn controller 50b that performs turn control.

[0039] The reaction force controller 50a includes a steering angle calculator 51, a steering reaction force command value calculator 52, and a power supply controller 53. The steering angle calculator 51 is based on the rotation angle θ of the reaction force motor 31 detected by the rotation angle sensor 33. a To calculate the steering angle θ of steering wheel 11 s .

[0040] Steering reaction force command value calculator 52 based on steering torque T h The steering reaction force command value T* is calculated using the vehicle speed V. The steering reaction force command value calculator 52 calculates the steering reaction force command value T*, ensuring its absolute value increases with the steering torque T. h The absolute value of the steering reaction force increases as the vehicle speed V decreases. The steering reaction force command value calculator 52 will be described in detail later.

[0041] The power supply controller 53 supplies power to the reaction force motor 31 corresponding to the steering reaction force command value T*. Specifically, the power supply controller 53 calculates the current command value for the reaction force motor 31 based on the steering reaction force command value T*. The power supply controller 53 uses a current sensor 54 installed in the power supply path of the reaction force motor 31 to detect the actual current I generated in that power supply path. a The value of current I. a The value is the actual current supplied to the reaction motor 31. The power supply controller 53 calculates the current command value and the actual current I. a The difference between the values ​​is controlled, and the power supply to the reaction force motor 31 is adjusted to eliminate this difference. Therefore, the reaction force motor 31 generates torque corresponding to the steering reaction force command value T*. Thus, the driver can be given an appropriate responsiveness based on the road reaction force.

[0042] The turning controller 50b includes a pinion angle calculator 61, a target pinion angle calculator 62, a pinion angle feedback controller 63, and a power supply controller 64. The pinion angle calculator 61 is based on the rotation angle θ of the turning motor 41 detected by the rotation angle sensor 43. b To calculate the pinion angle θ, which is the actual rotation angle of the pinion shaft 44. p The turning motor 41 and the pinion shaft 44 are interconnected via a reduction gear mechanism 42. Therefore, at the rotation angle θ of the turning motor 41... b With pinion angle θ p There is a correlation between them. This correlation can be used based on the rotation angle θ of the turning motor 41. b To calculate the pinion angle θ p The pinion shaft 44 meshes with the turning shaft 14. Therefore, at the pinion angle θ... p There is also a correlation with the amount of movement of the turning shaft 14. That is, the pinion angle θ p It reflects the turning angle θ of the turning wheel 16. w The value of .

[0043] The target pinion angle calculator 62 is based on the steering angle θ calculated by the steering angle calculator 51. s To calculate the target pinion angle θp * In this embodiment, the target pinion angle calculator 62 calculates the target pinion angle θ. p *Set to the steering angle θ s The same value. That is, as the turning angle θ. w With steering angle θ s The ratio of the steering angle is "1:1".

[0044] In addition, the target pinion angle calculator 62 can calculate the target pinion angle θ. p *Set to the steering angle θ s Different values. That is, the target pinion angle calculator 62 sets the turning angle θ according to the vehicle's driving state, such as the vehicle speed V. w With steering angle θ s The ratio of the steering angle is used to calculate the target pinion angle θ based on the set steering angle ratio. p * Target pinion angle calculator 62 calculates the target pinion angle θ p *, so that relative to the steering angle θ s Turning angle θ w It increases as the vehicle speed V decreases, and relative to the steering angle θ s Turning angle θ w The steering angle decreases as the vehicle speed V increases. To achieve the steering angle ratio set according to the vehicle's driving state, the target pinion angle calculator 62 calculates the steering angle θ. s The correction angle is calculated and then compared with the steering angle θ. s The targets are added together, and the target pinion angle θ is calculated based on the steering angle ratio. p *

[0045] The pinion angle feedback controller 63 receives the target pinion angle θ calculated by the target pinion angle calculator 62. p *and the actual pinion angle θ calculated by pinion angle calculator 61 p The pinion angle feedback controller 63 uses the pinion angle θ... p Feedback control is used to calculate the pinion angle command value T. p *, making the actual pinion angle θ p Following the target pinion angle θ p *

[0046] The power supply controller 64 will communicate with the pinion angle command value T. p *The corresponding power supply is sent to the turning motor 41. Specifically, the power supply controller 64 is based on the pinion angle command value T. p* This is used to calculate the current command value for the turning motor 41. The power supply controller 64 uses a current sensor 65 located in the power supply path of the turning motor 41 to detect the actual current I generated in that power supply path. b The value of current I. b The value is the actual current supplied to the turning motor 41. The power supply controller 64 calculates the current command value and the actual current I. b The difference between the values ​​is controlled, and the power supply to the turning motor 41 is adjusted to eliminate this difference. Therefore, the turning motor 41 rotates in accordance with the pinion angle command value T. p *Corresponding angle.

[0047] Configuration of the steering reaction force command value calculator

[0048] The configuration of the steering reaction force command value calculator 52 will be described below. For example... Figure 3 As shown, the steering reaction force command value calculator 52 includes a target steering reaction force calculator 71, an axial force calculator 72, and a subtractor 73.

[0049] Target Steering Reaction Force Calculator 71 Based on Steering Torque T h The target steering reaction force T1* is calculated based on the vehicle speed V. The target steering reaction force T1* is the target value of the torque generated by the reaction force motor 31, which acts in the opposite direction to the operation direction of the steering wheel 11. The target steering reaction force calculator 71 calculates the target steering reaction force T1* such that its absolute value increases as the absolute value of the steering torque Th increases and the vehicle speed V decreases.

[0050] Axial force calculator 72 based on pinion angle θ p The current I of the turning motor 41 b The axial force acting on the turning axle 14 via the turning wheel 16 is calculated using the value of the axial force and the vehicle speed V, and the converted torque value (the steering reaction force corresponding to the axial force) T2* is calculated by converting the calculated axial force into torque.

[0051] Subtractor 73 calculates the steering reaction force command value T* by subtracting the converted torque value T2* calculated by axial force calculator 72 from the target steering reaction force T1* calculated by target steering reaction force calculator 71.

[0052] Configuration of axial force calculator

[0053] The configuration of the axial force calculator 72 will be described in detail below. The axial force calculator 72 includes a basic axial force calculator 81, a limiting axial force calculator 82, an adder 83, and a converter 84.

[0054] The basic axial force calculator 81 calculates the basic axial force F1 as the basic axial force acting on the turning shaft 14 via the turning wheel 16. The basic axial force F1 is one of the following three axial forces (A1) to (A3).

[0055] (A1) Angle Axial Force

[0056] The axial force is, for example, related to the pinion angle θ. p The corresponding axial force. Basic axial force calculator 81 based on pinion angle θ. p Calculate the axial force at an angle. The basic axial force calculator 81 calculates the axial force at an angle such that its value changes with the pinion angle θ. p The absolute value of the axial force increases as the vehicle speed V decreases. The absolute value of the axial force increases with the pinion angle θ. p The axial force increases linearly with the increase of its absolute value. The angular axial force is set to be proportional to the pinion angle θ. p The symbols are the same. Angular axial force is an axial force that does not react to road conditions or is exerted on the turning axle 14 via the turning wheel 16.

[0057] (A2) Axial force of current

[0058] The axial force of the current is related to the current I of the turning motor 41. b The value corresponds to the axial force. The basic axial force calculator 81 is based on the current I of the turning motor 41. b The value of I is used to calculate the axial force of the current. The current I of the turning motor 41... b The value is affected by the road surface conditions acting on the turning wheel 16, such as the road surface friction resistance, and depends on the target pinion angle θ. p * and actual pinion angle θ p The difference between them changes. That is, the actual road surface condition acting on the turning wheel 16 is reflected in the current I of the turning motor 41. b The value can be determined based on the current I of the turning motor 41. b The value is used to calculate the axial force reflecting the influence of road surface conditions. The basic axial force calculator 81, for example, calculates the current I of the turning motor 41. b The value is multiplied by a gain that corresponds to the vehicle speed V to calculate the current axial force. The current axial force is the axial force that reflects the road surface condition or the force acting on the turning axle 14 via the turning wheel 16.

[0059] (A3) Mixed axial force

[0060] The mixed axial force is an axial force that combines angular axial force and current axial force in a predetermined ratio. The Basic Axial Force Calculator 81 sets the distribution ratio of angular axial force and current axial force separately based on various state variables reflecting vehicle behavior, road surface conditions, or steering conditions. The Basic Axial Force Calculator 81 calculates the mixed axial force by summing the values ​​obtained by multiplying the angular axial force and current axial force by the separately set distribution ratio.

[0061] The axial force limiting calculator 82 calculates the limiting axial force F2 used to virtually limit the operating range of the steering wheel 11. The limiting axial force F2 is at least one of the following two axial forces (B1) and (B2).

[0062] (B1) Axial force at the end

[0063] The end axial force is calculated based on the following principle: when the steering wheel 11 approaches the limit position of its operating range, or when the steering shaft 14 approaches the limit position of its physical range of motion, the torque generated from the reaction force motor 31 in the direction opposite to the steering direction increases rapidly. The limit position of the steering wheel 11's operating range is determined, for example, based on the length of the spiral cable provided in the steering wheel 11. The limit position of the steering shaft 14's physical range of motion is the position that physically limits the range of motion of the steering shaft 14 due to the occurrence of so-called "end contact," in which the rack end, as the end of the steering shaft 14, contacts the housing (not shown). The axial force limiting calculator 82 is based, for example, on the pinion angle θ. p and steering angle θ s To calculate the axial force at the end.

[0064] (B2) Curbstone axial force

[0065] The curb axial force is the axial force transmitted to the driver, for example, when the vehicle starts from a stationary position and the turning wheel 16 contacts an obstacle such as a curb via steering reaction force. The curb axial force is calculated based on the following: when the turning wheel 16 contacts an obstacle, the torque generated from the reaction force motor 31 in the opposite direction to the steering direction is rapidly increased to limit additional turning or return steering. The axial force limiting calculator 82 determines whether the turning wheel 16 is in contact with an obstacle such as a curb. When it is determined that the turning wheel 16 is in contact with an obstacle such as a curb, the axial force limiting calculator 82, for example, is based on the steering angle θ. s Calculate the axial force on the curbstone.

[0066] Adder 83 calculates the final axial force F3 by adding the basic axial force F1 calculated by the basic axial force calculator 81 to the limiting axial force F2 calculated by the limiting axial force calculator 82. This final axial force F3 is the final axial force used to calculate the steering reaction force command value T*. Adder 83 corresponds to the final axial force calculator.

[0067] The converter 84 calculates the converted torque value T2* by converting the final axial force F3 calculated by the adder 83 into torque. Here, it is envisioned that the limiting axial force calculator 82 employs a configuration for separately calculating the limiting axial force F2 as the end axial force and the limiting axial force F2 as the curb axial force. However, when using this configuration, it may be necessary to perform a process of adjusting the end axial force and the curb axial force. According to product specifications, it is envisioned that the axial force with the larger absolute value between the end axial force and the curb axial force be selected as the limiting axial force F2 to suppress the calculation of the final axial force F3 with an excessively large calculated value. To provide the driver with a more appropriate steering feel, it is also envisioned that at least one value of the basic axial force F1 and the limiting axial force F2 be adjusted according to the vehicle's steering or driving state.

[0068] There is a need to reduce the computational load in control device 50. One reason why reducing the computational load of the limiting axial force calculator 82 is hindered in this regard is that the limiting axial force calculator 82 calculates both the end axial force and the curb axial force separately and performs the process of adjusting the end axial force and the curb axial force. There is concern about an increase in the computational load of the limiting axial force calculator 82.

[0069] Therefore, in this embodiment, the axial force calculator 82 is configured as follows. For example... Figure 4 As shown, the axial force limiting calculator 82 includes a determiner 90, a steering angle holder 91, a difference calculator 92, a reference angle calculator 93, a final difference calculator 94, a pre-limit axial force calculator 95, a gain calculator 96, a differentiator 97, a multiplier 98, and an adder 99.

[0070] Determiner 90 determines whether turning wheel 16 is in contact with an obstacle such as a curb. For example, determiner 90 determines that turning wheel 16 is in contact with an obstacle such as a curb when all four determination conditions (C1) to (C4) are met.

[0071] (C1)|Δθ p (=|θ p * -θ p |)|>θ pth

[0072] (C2)|I b |>Ith

[0073] (C3)|ω p |<ω th

[0074] (C4)|V| <V th

[0075] In the given condition (C1), “θ p * indicates the target pinion angle calculated by the target pinion angle calculator 62. "θ" p "Δθ" represents the pinion angle calculated by the pinion angle calculator 61. p "It is achieved by measuring the target pinion angle θ" p *Subtract the actual pinion angle θ p The angle difference obtained. "θ" pth "" represents the angle difference threshold. The angle difference threshold θ is set based on the following viewpoints. pth That is, when the turning wheel 16 contacts an obstacle, it is difficult to turn the turning wheel 16 to an additional turn steering side or a return steering side. When the steering wheel 11 is turned to the additional turn steering side or the return steering side in this state, the target pinion angle θ p *Increases with steering, and the turning angle θ w Or pinion angle θ p It remains at a fixed value. Therefore, when the turning wheel 16 contacts an obstacle, the target pinion angle θ will cause the turning wheel 16 to turn additionally. p *With pinion angle θ p The difference between them increases. Therefore, it can be said that as the angle difference Δθ increases... p As the absolute value of the angle increases, the turning wheel 16 is more likely to come into contact with the obstacle. Therefore, the angle difference Δθ p This value indicates the probability that the turning wheel 16 will come into contact with an obstacle. Based on this, and taking into account tolerances caused by noise, etc., of the rotation angle sensor 43, the angle difference threshold θ is set through experimentation or simulation. pth .

[0076] In determining condition (C2), "I" b "This indicates the current I of the turning motor 41" b The value of "I". th "" indicates the current threshold. The current threshold I is set based on the following viewpoints. th That is, when the turning wheel 16 contacts an obstacle, the current I of the turning motor 41... bThe absolute value of increases as the turning wheel 16 will be turned additionally. Therefore, it can be said that as the current I of the turning motor 41 increases... b The absolute value of the current increases, making it more likely that the turning wheel 16 will come into contact with an obstacle. Therefore, the current I of the turning motor 41 increases. b The value also indicates the probability of the turning wheel 16 contacting an obstacle. Based on this, the current threshold I is set through experimentation or simulation. th .

[0077] Under the given condition (C3), “ω p "" represents the angular velocity of the pinion, and is expressed by the angle θ of the pinion. p It is obtained by differentiation. "ω" th "" indicates the angular velocity threshold. The angular velocity threshold ω is set based on the following viewpoints. th That is, when the turning wheel 16 is in contact with an obstacle, it is difficult to make the turning wheel 16 turn. Therefore, it can be said that as the turning speed of the turning wheel 16 decreases and the angular velocity ω of the pinion decreases... p As the absolute value decreases, the turning wheel 16 is more likely to come into contact with the obstacle. Therefore, the pinion angular velocity ω p This value also indicates the probability of the turning wheel 16 contacting an obstacle. Based on this, and considering tolerances caused by noise from the rotation angle sensor 43, the angular velocity threshold ω is set through experimentation or simulation. th .

[0078] In condition (C4), "V" represents the vehicle speed detected by vehicle speed sensor 501. th "V" represents the vehicle speed threshold, which is used as a benchmark to determine whether a vehicle is traveling at a low speed. Vehicle speed threshold V th The vehicle speed threshold V is set using a low speed range (0 km / h to below 40 km / h) and is, for example, set to "40 km / h". The vehicle speed threshold V is set based on the following viewpoint: th : Determine whether the turning wheel 16 is in contact with an obstacle, or whether the current driving state is a driving state that correctly notifies the driver that the turning wheel 16 is in contact with an obstacle by rapidly changing the steering reaction force.

[0079] The determiner 90 sets the value of flag F based on the determination of whether the turning wheel 16 is in contact with an obstacle. When it is determined that the turning wheel 16 is not in contact with an obstacle, that is, when at least one of the four determination conditions (C1) to (C4) is not met, the determiner 90 sets the value of flag F to "0". When it is determined that the turning wheel 16 is in contact with an obstacle, that is, when all of the four determination conditions (C1) to (C4) are met, the determiner 90 sets the value of flag F to "1".

[0080] Steering angle retainer 91 receives the value of flag F set by determiner 90 and steering angle θ calculated by steering angle calculator 51. s When the determiner 90 determines that the turning wheel 16 is in contact with an obstacle, that is, when the value of the flag F set by the determiner 90 is "1", the steering angle holder 91 maintains the current steering angle θ. s The turning angle θ is determined by the curb. s 1. As represented by the following expression (D1). This is for determining the turning angle θ using the curb. s 1 is used as the starting point for the generation of the axial force of the curbstone, in order to generate the force relative to the turning angle θ. s Determine the turning angle θ relative to the curb. s The change in 1 corresponds to the axial force of the curb. When the determiner 90 determines that the turning wheel 16 is not in contact with the obstacle, that is, when the value of the flag F set by the determiner 90 is "0", the steering angle holder 91 does not maintain the steering angle θ. s The steering angle retainer 91 holds the current steering angle θ. s As a non-curbstone, the steering angle θ is determined. s 1. Supply to the reference angle calculator 93. That is, when the value of the flag F is "0", the steering angle θ s 1 has the same turning angle θ at that time. s Same value.

[0081] θ s 1 = θ s …(D1)

[0082] The difference calculator 92 receives the value of the flag F set by the determiner 90 and the pinion angle θ calculated by the pinion angle calculator 61. p pinion angle θ p It reflects the turning angle θ of the turning wheel 16. w The value of the flag F set by the determiner 90 is "1". The difference calculator 92 maintains the current turning angle θ. w As a curbstone, determine the turning angle θ w 1, as represented by the following expression (D2). Furthermore, the difference calculator 92 can be based on the pinion angle θ. p Calculate the turning angle θ w .

[0083] θ w 1 = θ w …(D2)

[0084] When the value of flag F set by the determiner 90 is "1", the difference calculator 92 calculates the curb to determine the turning angle θ. w 1 and the current turning angle θ w The difference Δθ betweenw As represented by the following expression (D3). This is for passing through the turning angle θ w Determining the turning angle θ from the curb. w The change in 1 updates the starting position of the axial force generation of the curbstone, that is, the curbstone determines the turning angle θ. s 1.

[0085] Δθ w =θ w -θ w 1…(D3)

[0086] When the value of flag F set by the determiner 90 is “0”, the difference calculator 92 does not maintain the turning angle θ. w The value of the flag F. When the value of the flag F is “0”, the difference calculator 92 does not calculate the difference Δθ based on expression (D3). w .

[0087] The reference angle calculator 93 receives the curb-determined or non-curb-determined steering angle θ from the steering angle retainer 91. s 1. The difference Δθ calculated using the difference calculator 92 w and the virtual end angle θ stored in the storage device of the control device 50 e Virtual end angle θ e It is the steering angle θ corresponding to the limit position of the virtual operating range of the steering wheel 11. s Or the pinion angle θ corresponding to the limiting position of the virtual operating range of the turning axle 14. p The steering angle θ is based on the position of the steering wheel 11 when its rotational position reaches the limit of its virtual operating range. s Use nearby values ​​to set the virtual end angle θ e Or, based on the pinion angle θ when the turning axle 14 reaches the limit position of its operating range. p Use nearby values ​​to set the virtual end angle θ e .

[0088] The limiting axial force calculator 82 may include being configured to calculate a virtual end angle θ based on vehicle speed V. e A calculator. For example, this calculator calculates the virtual end angle θ. e This causes its absolute value to decrease as the vehicle speed V increases.

[0089] When the curbstone is input, the steering angle θ is determined. s At time 1, the reference angle calculator 93 calculates the difference Δθ. w With input steering angle θ s 1. Add them together to calculate the reference angle θ hold As can be represented by the following expression (4). Reference angle θ hold By using the turning angle θw Determining the turning angle θ from the curb. w The change in 1 updates the curbstone and determines the turning angle θ. s The value obtained is 1.

[0090] θ hold =θ s 1+Δθ w …(D4)

[0091] In addition, when the non-curbstone is input to determine the steering angle θ s At time 1, the reference angle calculator 93 will input the steering angle θ. s 1. Set the reference angle θ without any changes. hold This is because the difference Δθ is based on expression (D3). w It was not calculated, meaning that when it was determined that the turning wheel 16 was not in contact with the obstacle, the difference Δθ w The value is "0".

[0092] Reference Angle Calculator 93 is based on virtual end angle θ e By using the reference angle θ hold Perform a constraint process to calculate the final reference angle θ hold 1. As represented by the following expression (D5). This is so that when the position of the steering wheel 11 or the position of the turning axle 14 reaches the virtual end angle θ e The axial force of the curbstone is generated at that time. "GRD()" in expression (D5) indicates the constraint process.

[0093] θ hold 1 = GRD(θ) hold ,θ e (D5)

[0094] The reference angle calculator 93 will display the virtual end angle θ. e Values ​​and reference angle θ hold The values ​​are compared. When the reference angle θ hold The value is greater than the virtual end angle θ e When the value is given, the reference angle calculator 93 will calculate the reference angle θ. hold The value is limited to the virtual end angle θ e The value of θ. When the reference angle θ hold The value is equal to or less than the virtual end angle θ e At that time, the reference angle calculator 93 will use expression (D4) to calculate the reference angle θ. hold The final reference angle θ is calculated without any changes. hold 1.

[0095] Final difference calculator 94 receives the final reference angle θ calculated by reference angle calculator 93. hold1 and the steering angle θ calculated by the steering angle calculator 51 s The final difference calculator 94 also receives the virtual end angle θ stored in the storage device of the control device 50. e And the value of flag F set by determiner 90. Final difference calculator 94 calculates the final reference angle θ. hold 1 and the current steering angle θ s The difference Δθ between them is represented by the following expression (D6).

[0096] Δθ=θ s -θ hold 1…(D6)

[0097] The final difference calculator 94, for example, corrects the difference Δθ according to the following three cases (E1) to (E3). w The value is used to calculate the final reference angle θ. hold 1 and the current steering angle θ s The final difference between them is Δθ1.

[0098] (E1) Curbstone determination not performed

[0099] When it is determined that the turning wheel 16 is not in contact with the obstacle, that is, when the value of the flag F is “0”, the final difference calculator 94 will set the difference Δθ calculated using expression (D6) as the final difference Δθ1 without any change, as represented by the following expression (D7).

[0100] Δθ1=Δθ…(D7)

[0101] (E2) Execute curbstone determination

[0102] When it is determined that the turning wheel 16 is in contact with an obstacle, that is, when the value of flag F is "1", the final difference calculator 94 corrects the difference Δθ calculated using expression (D6) to a smaller value. For example, the final difference calculator 94 corrects the value of difference Δθ to the value "1 / 2" or "1 / 3". The final difference calculator 94 sets the corrected difference Δθ2 as the final difference Δθ1, as represented by the following expression (D8). This is to reproduce the slow increase in the reaction force of the tire's elastic deformation when the turning wheel 16 makes an additional turn while in contact with the obstacle.

[0103] Δθ1=Δθ2…(D8)

[0104] (E3) Determine the curbstone and the end of the road.

[0105] Final difference calculator 94, for example, by comparing the steering angle θ s With virtual end angle θ eTo perform end determination of whether the rotational position of the steering wheel 11 has reached the limit position of its virtual operating range.

[0106] When it is determined that the turning wheel 16 is in contact with an obstacle and the rotational position of the steering wheel 11 reaches the limit position of its virtual operating range, the final difference calculator 94 performs the following process.

[0107] That is, the final difference calculator 94 corrects the difference Δθ calculated using expression (D6) to a smaller value. For example, the final difference calculator 94 corrects the value of the difference Δθ to the value "1 / 2" or "1 / 3". The final difference calculator 94 temporarily sets the corrected difference Δθ2 as the first final difference Δθ1, as represented by the following expression (D9).

[0108] Δθ1=Δθ2…(D9)

[0109] As shown in the following expression (D10), the final difference calculator 94 calculates the steering angle θ. s With virtual end angle θ e The difference between them is calculated and the calculated difference is temporarily set as the second final difference Δθ1.

[0110] Δθ1=θ s -Δθ e …(D10)

[0111] The final difference calculator 94 selects the larger of the first final difference Δθ1 calculated using expression (D9) and the second final difference Δθ1 calculated using expression (D10).

[0112] The pre-limiting axial force calculator 95 calculates the pre-limiting axial force F21 based on the final difference Δθ1 calculated by the final difference calculator 94. The pre-limiting axial force calculator 95 uses the limiting axial force mapping stored in the storage device of the control device 50 to calculate the pre-limiting axial force F21.

[0113] like Figure 5 As shown in the graph, the limiting axial force mapping M1 is a two-dimensional mapping where the horizontal axis is set to the final difference Δθ1 and the vertical axis is set to the pre-limiting axial force F21. The pre-limiting axial force F21 has the following characteristics: As indicated by the characteristic line L1, the value of the pre-limiting axial force F21 is set to a larger value as the value of the final difference Δθ1 increases. The slope, i.e., the rate of change of the pre-limiting axial force F21 relative to the final difference Δθ1, gradually increases as the value of the final difference Δθ1 increases. That is, the characteristic line L1 is a curve with a positively increasing slope.

[0114] When it is determined that the turning wheel 16 is in contact with an obstacle (cases E2 and E3), the difference Δθ calculated using expression (D6) is corrected to a smaller value. The relationship between the final difference Δθ1 and the pre-limiting axial force F21 at that time is the same as indicated by characteristic line L2. Characteristic line L2 indicates the relationship between the final difference Δθ1 and the pre-limiting axial force F21 if the value of the difference Δθ calculated using expression (D6) is not corrected to a smaller value. Characteristic line L2 is a curve with a positively increasing slope. The slope of characteristic line L2 is generally less than the slope of characteristic line L1. That is, when it is determined that the turning wheel 16 is in contact with an obstacle, the pre-limiting axial force calculator 95 uses the limiting axial force diagram M1, in which the gradient of the characteristic line slows down by delaying characteristic line L1 along the horizontal axis, to calculate the pre-limiting axial force F21.

[0115] The pre-limiting axial force calculator 95 corresponds to the axial force calculator that calculates the limiting axial force (pre-limiting axial force F21) used to virtually limit the operation of the steering wheel 11 based on the value of the final difference Δθ1.

[0116] The gain calculator 96 calculates the damping gain G based on the final difference Δθ1 calculated by the final difference calculator 94. The gain calculator 96 uses the gain mapping M2 stored in the storage device of the control device 50 to calculate the damping gain G.

[0117] like Figure 6 As shown in the graph, gain mapping M2 is a mapping where the horizontal axis is set to the final difference Δθ1 and the vertical axis is set to the gain G. Gain mapping M2 has the following characteristics: As the value of the final difference Δθ1 increases, the value of the pre-limiting axial force F21 is set to a larger value. As the value of the final difference Δθ1 increases, the slope, i.e., the rate of change of gain G relative to the final difference Δθ1, gradually increases.

[0118] Differentiator 97 receives the steering angle θ calculated by steering angle calculator 51. s And by receiving the steering angle θ s To calculate the steering angular velocity ω, perform differentiation. s Multiplier 98 uses the steering angular velocity ω calculated by differentiator 97. s The damping axial force F22 is calculated by multiplying it by the gain G calculated by the gain calculator 96. The reason for calculating the damping axial force is as follows: as the gradient of the pre-constraint axial force F21 relative to the final difference Δθ1 increases, the value of the pre-constraint axial force F21 oscillates with changes in the final difference Δθ1. Therefore, the damping axial force F22 is calculated to stabilize the value of the pre-constraint axial force F21 relative to the final difference Δθ1.

[0119] Adder 99 calculates the final limiting axial force F2 by adding the pre-limiting axial force F21 calculated by pre-limiting axial force calculator 95 to the damping axial force F22 calculated by multiplier 98.

[0120] Operation of the implementation method

[0121] The operation in this embodiment will now be described. When the steering wheel 11 is not in a position near the limit of its operating range, or when the turning axle 14 is not in a position near the limit of its physical range of motion, the limiting axial force calculator 82 essentially does not calculate the limiting axial force F2. When it is determined that the turning wheel 16 is in contact with an obstacle, the limiting axial force calculator 82 essentially does not calculate the limiting axial force F2. Therefore, the basic axial force F1 calculated by the basic axial force calculator 81 is used as the final axial force F3. In this case, a steering reaction force corresponding to the vehicle behavior or road condition can be applied to the steering wheel 11 by reflecting the converted torque value T2* obtained by converting the final axial force F3 into torque in the steering reaction force command value T*. The driver can determine the vehicle behavior or road condition by feeling the steering reaction force from the steering wheel 11 as a response.

[0122] When the steering wheel 11 has reached its operating range limit position or when the steering shaft 14 has reached its physical movement range limit position, the limiting axial force calculator 82 calculates the limiting axial force F2 as the end axial force corresponding to the final difference Δθ1. Therefore, the value obtained by adding the limiting axial force F2 as the end axial force and the basic axial force F1 is used as the final axial force F3. In this case, the steering reaction force increases rapidly by reflecting the converted torque value T2* obtained by converting the final axial force F3 into torque in the steering reaction force command value T*. Therefore, it is difficult for the driver to move along the steering angle θ. s The direction in which the absolute value of the steering wheel increases is the direction of the steering wheel operation. Therefore, by feeling the contact sensation as the steering reaction force (response), the driver can identify whether the steering wheel 11 has reached the limit position of the virtual operating range, or whether the turning axle 14 has reached the limit position of the physical range of movement.

[0123] When additional turning or return turning is performed while the turning wheel 16 is in contact with an obstacle, the limiting axial force calculator 82 calculates the limiting axial force F2 as the curb axial force corresponding to the final difference Δθ1. Therefore, the value obtained by adding the limiting axial force F2 as the curb axial force and the basic axial force F1 is used as the final axial force F3. In this case, the steering reaction force increases rapidly by reflecting the converted torque value T2* obtained by converting the final axial force F3 into torque in the steering reaction force command value T*. Therefore, it is difficult for the driver to perform additional turning or return turning. Therefore, by feeling the contact sensation as the steering reaction force (response), the driver can identify that the turning wheel 16 is in contact with an obstacle such as a curb. Furthermore, compared to the limiting axial force F2 as an end axial force, the limiting axial force F2 as the curb axial force increases slowly with the increase of the final difference Δθ1. Therefore, the driver can feel a response closer to the actual situation in which the turning wheel 16 is being additionally turned via the steering wheel 11 while the turning wheel 16 is in contact with an obstacle.

[0124] Advantages of the implementation method

[0125] Therefore, according to this embodiment, the following advantages can be achieved. Based on the reference angle θ calculated according to whether the turning operation of the turning wheel 16 is restricted... hold With the current steering angle θ s The difference between the two forces is used to calculate one of the limiting axial force F2 as the curb axial force and the limiting axial force F2 as the end axial force. The limiting axial force F2 as the curb axial force is the axial force used to limit new operations of the steering wheel 11 when the turning operation of the turning wheel 16 is restricted. The end axial force is the axial force used to limit steering beyond the virtual end angle of the steering wheel 11. That is, the calculation of the limiting axial force F2 as the curb axial force and the limiting axial force F2 as the end axial force are shared. Therefore, the process of adjusting the curb axial force and the end axial force is not required. Therefore, the computational load can be reduced compared to the case of calculating the curb axial force and the end axial force separately.

[0126] When the turning wheel 16 is forced to turn additionally while its turning operation is restricted, the reaction force increases slowly due to the elastic deformation of the tire. When the turning operation of the turning wheel 16 is restricted, the value of the final difference Δθ1 calculated by the final difference calculator 94 is corrected to a smaller value. Therefore, the steering reaction force can be increased more slowly. Thus, a steering reaction force closer to the actual state in which the turning operation of the turning wheel 16 is restricted can be applied to the steering wheel 11.

[0127] When the turning operation of the steering wheel 16 is restricted, and the rotation position of the steering wheel 11 has reached the limit position of the virtual operating range, the final difference calculator 94 uses the larger of the two final differences Δθ1 calculated for each case. Therefore, the steering reaction force corresponding to the larger final difference Δθ1 can be applied to the steering wheel 11.

[0128] As the gradient of the change in the limiting axial force F2 relative to the final difference Δθ1 increases, the value of the pre-limiting axial force F21 or the limiting axial force F2 will oscillate with the change in the value of the final difference Δθ1. At this point, the value of the pre-limiting axial force F21 or the final axial force F2 can be stabilized relative to the final difference Δθ1 by reflecting the damping axial force F22 in the pre-limiting axial force F21.

[0129] Even when the turning operation of the turning wheel 16 is restricted, the turning wheel 16 may still turn slightly. At this point, the steering angle θ held by the steering angle retainer 91... s The amount of turning is corrected based on the turning of the turning wheel 16. This is based on the corrected steering angle θ. s To calculate the reference angle θ hold Therefore, even when the turning wheel 16 is turned under conditions where its turning operation is restricted, a more appropriate steering reaction force can be applied to the steering wheel 11.

[0130] Other implementation methods

[0131] This implementation can be modified as follows: The axial force limiting calculator 82 can be configured to use an abbreviated difference calculator 92. In this case, the reference angle calculator 93 determines the steering angle θ from the curb. s 1. Set the reference angle θ without any changes. hold .

[0132] The limiting axial force calculator 82 can be configured such that the gain calculator 96, differentiator 97, multiplier 98, and adder 99 are omitted. In this case, the pre-limiting axial force F21 calculated by the pre-limiting axial force calculator 95 is used as the final limiting axial force F2 without any change. The pre-limiting axial force calculator 95 corresponds to the axial force calculator that calculates the pre-limiting axial force F21 as the final limiting axial force F2 based on the value of the final difference Δθ1.

[0133] The final difference calculator 94 can skip reducing the reference angle θ when determining the curb. hold With the current steering angle θ s The correction of the value of the difference Δθ between them. The clutch can be set in the steering system 10. In this case, as by Figure 1The double-dotted line indicates that the steering shaft 12 and pinion shaft 13 are connected via clutch 21. Clutch 21 is an electromagnetic clutch that transmits and disconnects power by allowing or disabling the supply of electricity to the excitation coil. Control unit 50 performs engagement / disengagement control to switch clutch 21 between engagement and disengagement. When clutch 21 is disengaged, the power transmission path between steering wheel 11 and steering wheel 16 is mechanically cut off. When clutch 21 is engaged, the power transmission path between steering wheel 11 and steering wheel 16 is mechanically established.

[0134] The left and right turning wheels 16 can turn independently. In this case, the control device 50 turns the turning wheels 16 by controlling the turning motor installed in the turning wheels 16.

Claims

1. A steering control device (50) that controls a reaction force motor (31) configured to generate a steering reaction force based on a command value calculated according to a steering state, the steering reaction force being applied to a steering wheel (11) whose power transmission path to and from the steering wheel (11) via a steering axle (14) that turns a steering wheel (16) is interrupted, the steering control device (50) characterized in that it comprises: A foundation axial force calculator (81) is configured to calculate the foundation axial force, which includes the following axial forces: The axial force reflects the force acting on the steering axle (14) via at least the steering wheel (16) when the steering wheel (11) is operated within a predetermined operating range; A limiting axial force calculator (82) is configured to calculate a limiting axial force, which is an axial force used to virtually limit the operation of the steering wheel (11); as well as A final axial force calculator (83) is configured to calculate a final axial force based on the base axial force and the limiting axial force, the final axial force being the final axial force to be reflected in the command value. The limiting axial force calculator (82) includes a steering angle retainer (91), a reference angle calculator (93), a final difference calculator (94), and an axial force calculator (95). The steering angle retainer (91) is configured to maintain the steering angle at which the turning operation is restricted when the turning operation of the turning wheel (16) is restricted. The reference angle calculator (93) is configured to calculate the reference angle by performing a limiting process that restricts the steering angle held by the steering angle holder (91) to a virtual end angle when the turning operation of the turning wheel (16) is restricted. The reference angle calculator (93) is configured to calculate the reference angle by performing a limiting process that restricts the current steering angle to the virtual end angle when the turning operation of the turning wheel (16) is not restricted. The virtual end angle corresponds to the limiting position of the virtual operating range of the steering wheel. The final difference calculator (94) is configured to calculate the final difference, which is the final difference between the reference angle and the current steering angle. The axial force calculator (95) is configured to calculate the limiting axial force based on the value of the final difference.

2. The steering control device (50) according to claim 1, characterized in that, The final difference calculator (94) is configured to correct the calculated final difference value to a smaller value when the turning operation of the turning wheel (16) is restricted.

3. The steering control device (50) according to claim 1 or 2, characterized in that, The final difference calculator (94) is configured to use the larger of the final difference calculated based on the premise that the turning operation of the turning wheel (16) is restricted and the rotation position of the steering wheel (11) reaches the limit position of the virtual operating range when the turning operation of the turning wheel (16) is restricted and the rotation position of the steering wheel (11) reaches the limit position of the virtual operating range.

4. The steering control device (50) according to claim 1 or 2, characterized in that, Also includes: A gain calculator (96) is configured to calculate the damping gain of the limiting axial force based on the value of the final difference calculated by the final difference calculator (94); as well as A multiplier (98) is configured to calculate the damping axial force to be reflected in the limiting axial force by multiplying the gain calculated by the gain calculator (96) by the steering angular velocity.

5. The steering control device (50) according to claim 1 or 2, characterized in that, It also includes a difference calculator (92), which is configured to calculate the difference between the turning angle of the turning wheel (16) when the turning operation of the turning wheel (16) is restricted and the current turning angle. The reference angle calculator (93) is configured to: when the turning operation of the turning wheel (16) is restricted, correct the steering angle held by the steering angle holder (91) based on the value of the difference calculated by the difference calculator (92), and calculate the reference angle by performing the restriction process on the corrected steering angle.

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