Steering controls

Abstract

A steering control device (50) is provided. The steering control device (50) includes a first calculator (81B) configured to calculate a first axial force, a second calculator (81A), and a third calculator (81C) configured to calculate a third axial force. The third calculator (81C) is configured to reduce the degree to which the first axial force is reflected in the third axial force and increase the degree to which the second axial force is reflected in the third axial force when a specific situation occurs in which the current of the turning motor (41) must be limited.

Description

Technical Field

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

[0002] A so-called steer-by-wire steering system is known that separates the power transmission between the steering wheel and the turning wheels. The steering system includes a reaction force motor as a source of steering reaction force applied to the steering shaft, and a turning motor as a source of turning force to turn the turning wheels. While the vehicle is traveling, a steering system control device generates a steering reaction force using the reaction force motor and turns the turning wheels using the turning motor.

[0003] In steer-by-wire systems, the power transmission between the steering wheel and the turning wheels is separated. Therefore, the road reaction force acting on the turning wheels is difficult to transmit to the steering wheel. As a result, the driver is less likely to feel the road conditions responding through the steering wheel.

[0004] Therefore, for example, the control device described in Japanese Unexamined Patent Application Publication No. 2017-165219 (JP2017-165219A) calculates an ideal axial force, which is an ideal rack axial force based on a target turning angle, and a road surface axial force, which is an estimated value of the rack axial force based on the current value of the turning motor. The control device adds the ideal axial force and the road surface axial force at a predetermined distribution ratio and controls the reaction force motor by using a basic reaction force based on the added axial force. Since the road surface condition is reflected in the road surface axial force, the road surface condition is also reflected in the steering reaction force generated by the reaction force motor. Therefore, the driver can feel the road surface condition as the steering reaction force. Summary of the Invention

[0005] Conventional steer-by-wire steering systems (including the one described in JP2017-165219A) are equipped with various protection features depending on the product specifications. One example of such protection is overheat protection for the turning motor. A control device with this function monitors the temperature of the turning motor and, if the monitored temperature approaches an overheating condition, limits the current supplied to the turning motor. This protects the turning motor.

[0006] However, when a control device that reflects the road axial force in the steering reaction force, as in JP2017-165219A, is equipped with an overheat protection function for the turning motor, the following limitations may arise. Specifically, the road axial force is calculated by multiplying the turning motor's current by a predetermined coefficient. Therefore, when the turning motor's current is limited based on the overheat protection of the turning motor, the road axial force, and therefore the steering reaction force, may decrease as the current is limited. Therefore, for example, while the steering reaction force must be further increased as information for the driver is provided, the following limitations may arise: The implementation of the turning motor's overheat protection function may not ensure the initially required steering reaction force.

[0007] The present invention provides a steering control device capable of ensuring a steering reaction force as information for a driver even when the current of a turning motor is limited.

[0008] The present invention relates to a steering control device. The steering control device controls a reaction force motor based on a command value calculated according to a steering condition. The reaction force motor is the source of the steering reaction force applied to the steering wheel, which is separated from the turning axis in terms of power transmission. The steering control device includes: a first calculator configured to calculate a first axial force acting on the turning axis based on a current value of a turning motor that is the source of the turning force applied to the turning axis; a second calculator configured to calculate a second axial force acting on the turning axis based on other vehicle state variables different from the current value of the turning motor; and a third calculator configured to calculate a third axial force as a final axial force to be reflected in the command value based on the first and second axial forces. The third calculator is configured to reduce the degree to which the first axial force is reflected in the third axial force and increase the degree to which the second axial force is reflected in the third axial force in a specific situation in which the current of the turning motor must be limited.

[0009] When the turning motor current is limited, the first axial force calculated based on the turning motor current value can also be limited, thereby limiting the third axial force on which the first axial force is reflected. Therefore, there is a high possibility that the steering reaction force required initially cannot be ensured. To address this issue, the above configuration reduces the reflection of the first axial force in the third axial force when the turning motor current must be limited, while increasing the reflection of the second axial force. In other words, the second axial force becomes more dominant within the third axial force. The second axial force is less susceptible to the current limitation of the turning motor. Therefore, even when the turning motor current is limited, the steering reaction force, which serves as information for the driver, can be ensured.

[0010] In the steering control device, the third calculator may be configured to calculate the third axial force by adding a value obtained by multiplying the first and second axial forces by a distribution ratio. The distribution ratio may be set according to vehicle behavior, steering conditions, or road conditions. The third calculator may be configured to reduce the distribution ratio of the first axial force to the third axial force and increase the distribution ratio of the second axial force to the third axial force in specific circumstances where current to the turning motor must be limited.

[0011] With the above configuration, when a specific situation arises where the current of the turning motor must be limited, the degree to which the first axial force is reflected in the third axial force can be reduced by reducing the distribution ratio of the first axial force relative to the third axial force. Furthermore, when a specific situation arises where the current of the turning motor must be limited, the degree to which the second axial force is reflected in the third axial force can be increased by increasing the distribution ratio of the second axial force relative to the third axial force. Furthermore, the first and second axial forces can be gradually switched by increasing or decreasing the distribution ratio of the first and second axial forces. Thus, for example, the steering reaction force, serving as information for the driver, can be gradually ensured, depending on the severity of the specific situation where the current of the turning motor must be limited.

[0012] The steering control device may further include a fourth calculator configured to, in a specific situation where the current of the turning motor must be limited, calculate the distribution ratios of the first axial force and the second axial force for use during current limitation based on a predetermined starting point. The predetermined starting point may be a point at which the distribution ratio of the first axial force to the third axial force further decreases and the distribution ratio of the second axial force to the third axial force further increases. The third calculator may be configured to calculate the third axial force using the distribution ratio for use during current limitation calculated by the fourth calculator in a specific situation where the current of the turning motor must be limited.

[0013] Through the above configuration, when a specific situation occurs in which the current of the turning motor must be limited, the distribution ratio of the first axial force relative to the third axial force can be further reduced by using the distribution ratio used when the current is limited calculated by the fourth calculator to calculate the third axial force, while the distribution ratio of the second axial force relative to the third axial force can be further increased.

[0014] In the steering control device, the fourth calculator may be configured to set the distribution ratio of the first axial force to the third axial force to 0% and to set the distribution ratio of the second axial force to the third axial force to 100% when a specific situation occurs in which the current of the turning motor must be limited.

[0015] With this configuration, when the current of the turning motor must be limited, the first axial force calculated based on the turning motor current value is not used, and the second axial force calculated based on a vehicle state variable different from the turning motor current value is used as the third axial force. Therefore, even when the current of the turning motor is limited, a more appropriate steering reaction force can be ensured as information for the driver.

[0016] In the steering control device, the third calculator can be configured to calculate the first axial force as the third axial force as is when a specific situation in which the current of the turning motor must be limited does not occur, and to calculate the second axial force as the third axial force as is when a specific situation in which the current of the turning motor must be limited occurs.

[0017] With this configuration, when the current of the turning motor must be limited, the first axial force calculated based on the turning motor current value is not used. Instead, the second axial force calculated based on a vehicle state variable different from the turning motor current value is used as the third axial force. Therefore, even when the current of the turning motor is limited, a steering reaction force that serves as information for the driver can be maintained.

[0018] The steering control device may further include a turning controller configured to control the turning motor according to a steering condition. The turning controller may be configured to set a flag value indicating whether a specific condition requiring current limiting of the turning motor has occurred, based on whether a predetermined determination condition is satisfied. The third calculator may be configured to identify the specific condition requiring current limiting of the turning motor based on the flag value set by the turning controller.

[0019] With the above configuration, the third calculator does not need to determine whether a specific situation has occurred in which the current of the turning motor must be limited based on whether a predetermined determination condition is satisfied. Therefore, the calculation load of the third calculator can be reduced.

[0020] According to the steering control device of the present invention, even when the current of the turning motor is limited, the steering reaction force as information for the driver can be ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Features, advantages, technical significance, 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:

[0022] Figure 1 is a configuration diagram of a steer-by-wire steering device equipped with a steering control device according to a first embodiment;

[0023] Figure 2 is a block diagram of a control device according to a first embodiment;

[0024] Figure 3 is a block diagram of a steering reaction force command value calculator according to the first embodiment;

[0025] Figure 4 is a block diagram of an axial force calculator according to a second embodiment;

[0026] Figure 5 is a block diagram of a steering reaction force command value calculator according to a sixth embodiment; and

[0027] Figure 6 is a block diagram of an axial force calculator according to a seventh embodiment. DETAILED DESCRIPTION

[0028] First embodiment

[0029] Hereinafter, a first embodiment in which the steering control apparatus is implemented as a steer-by-wire type steering apparatus will be described.

[0030] like Figure 1 As shown, the steering device 10 of the vehicle has a steering shaft 12 connected to a steering wheel 11. In addition, the steering device 10 has a plurality of Figure 1 The left and right turning wheels 16 are connected to both ends of the turning shaft 14 via tie rods 15. The turning angle θ of the turning wheel 16 is w The steering axis 12 and the turning axis 14 form a steering mechanism of the vehicle.

[0031] The steering system 10 also includes a reaction force motor 31, a speed reduction mechanism 32, a rotation angle sensor 33, and a torque sensor 34 as components for generating a steering reaction force. The steering reaction force is a force applied by the driver in the direction opposite to the direction in which the steering wheel 11 is operated. Applying the steering reaction force to the steering wheel 11 provides the driver with an appropriate sense of response.

[0032] The reaction motor 31 is a source of steering reaction force. For example, a three-phase brushless motor is employed as the reaction motor 31. The rotation shaft of the reaction motor 31 is connected to the steering shaft 12 via a speed reduction mechanism 32. The torque of the reaction motor 31 is applied to the steering shaft 12 as the steering reaction force.

[0033] The rotation angle sensor 33 is provided 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 the steering angle θs The reaction force motor 31 and the steering shaft 12 are interlocked with each other via the speed reduction mechanism 32. Therefore, the rotation angle θ of the reaction force motor 31 a The rotation angle of the steering shaft 12 and the steering angle θ which is the rotation angle of the steering wheel 11 s Therefore, the rotation angle θ of the reaction force motor 31 can be used to determine the rotation angle θ of the reaction force motor 31. a To obtain the steering angle θ s .

[0034] The torque sensor 34 detects the steering torque T which is the torque applied to the steering shaft 12 by the rotation operation of the steering wheel 11. h The torque sensor 34 detects the steering torque T applied to the steering shaft 12 based on the twisting amount of the torsion bar provided in the middle of the steering shaft 12. h The torque sensor 34 is provided at a portion of the steering shaft 12 that is closer to the steering wheel 11 than the speed reduction mechanism 32 .

[0035] Furthermore, the steering device 10 has a turning motor 41 , a speed reduction mechanism 42 , and a rotation angle sensor 43 as a configuration for generating a turning force that is a power for turning the turning wheels 16 .

[0036] The turning motor 41 is a source of turning force. For example, a three-phase brushless motor is used as the turning motor 41. The rotation shaft of the turning motor 41 is connected to the 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 turning shaft 14. The torque of the turning motor 41 is applied to the turning shaft 14 via the pinion shaft 44 as a turning force. In response to the rotation of the turning motor 41, the turning shaft 14 moves along the axis of rotation. Figure 1 Movement in the vehicle width direction in the left and right directions.

[0037] The rotation angle sensor 43 is provided in the turning motor 41. The rotation angle sensor 43 detects the rotation angle θ of the turning motor 41. b . In addition, the steering device 10 has a pinion shaft 13. The pinion shaft 13 is arranged to intersect with the turning shaft 14. The pinion teeth 13a of the pinion shaft 13 are engaged with the rack teeth 14a of the turning shaft 14. The reason for providing the pinion shaft 13 is to support the turning shaft 14 together with the pinion shaft 44 in a housing (not shown). That is, the turning shaft 14 is movably supported in the axial direction by a supporting mechanism (not shown) provided in the steering device 10, and is pressed toward the pinion shafts 13 and 44. In this way, the turning shaft 14 is supported in the housing. Note that another supporting mechanism for supporting the turning shaft 14 on the housing may be provided without using the pinion shaft 13.

[0038] The steering device 10 also includes a control device 50. The control device 50 controls the reaction force motor 31 and the turning motor 41 based on the detection results of various sensors installed on the vehicle. In addition to the rotation angle sensor 33, torque sensor 34, and rotation angle sensor 43 described above, the sensors also include a vehicle speed sensor 501. The vehicle speed sensor 501 detects the vehicle speed V, which is the vehicle's running speed.

[0039] The control device 50 controls the reaction force motor 31 to generate the steering torque T h The control device 50 controls the reaction force of the corresponding steering reaction force based on the steering torque T h and the vehicle speed V to calculate the target steering reaction force, and calculate the steering reaction force command value based on the calculated target steering reaction force. The control device 50 supplies the current required to generate the steering reaction force to the reaction force motor 31 according to the steering reaction force command value.

[0040] The control device 50 controls the turning motor 41 to perform turning control for turning the turning wheel 16 according to the steering condition. The control device 50 performs turning control based on the rotation angle θ of the turning motor 41 detected by the rotation angle sensor 43. b The pinion angle θ is calculated as the actual rotation angle of the pinion shaft 44. p Pinion angle θ p is the turning angle θ of the turning wheel 16 w In addition, 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 Then, the control device 50 obtains the target pinion angle and the actual pinion angle θ p and controls the power feed to the turning motor 41 to eliminate the deviation.

[0041] Next, the control device 50 will be described in detail. Figure 2 As shown, the control device 50 includes a reaction force controller 50a that performs reaction force control and a turning controller 50b that performs turning control.

[0042] The reaction force controller 50a includes a steering angle calculator 51, a steering reaction force command value calculator 52, and an energization controller 53. The steering angle calculator 51 calculates the rotation angle θ of the reaction force motor 31 detected by the rotation angle sensor 33 based on the rotation angle θ of the reaction force motor 31. a To calculate the steering angle θ of the steering wheel 11 s .

[0043] The steering reaction force command value calculator 52 is based on the steering torque T h and the vehicle speed V to calculate the steering reaction force command value T * The steering reaction force command value calculator 52 calculates the steering torque T h The larger the absolute value of τ and the slower the vehicle speed V, the larger the absolute value of the steering reaction force command value T * The steering reaction force command value calculator 52 will be described in detail later.

[0044] The energized controller 53 is based on the steering reaction force command value T * Power is supplied to the reaction force motor 31. Specifically, the energization controller 53 supplies power to the reaction force motor 31 based on the steering reaction force command value T * The current command value for the reaction force motor 31 is calculated. In addition, the energization controller 53 detects the actual current I generated in the power feeding path of the reaction force motor 31 through the current sensor 54 provided in the power feeding path. a The value of current I a The value of is the actual current value supplied to the reaction force motor 31. Then, the energization controller 53 obtains the current command value and the actual current I a The deviation between the values ​​of and controls the power feed to the reaction force motor 31 to eliminate the deviation. In this way, the reaction force motor 31 is driven according to the steering reaction force command value T * Generates torque, giving the driver an appropriate sense of response corresponding to the reaction force of the road surface.

[0045] The turning controller 50b includes a pinion angle calculator 61, a target pinion angle calculator 62, a pinion angle feedback controller 63, a limit value controller 64, and an energization controller 65. The pinion angle calculator 61 calculates the rotation angle θ of the turning motor 41 detected by the rotation angle sensor 43. b The pinion angle θ is calculated as the actual rotation angle of the pinion shaft 44. p The turning motor 41 and the pinion shaft 44 are interlocked with each other through the speed reduction mechanism 42. Therefore, at the rotation angle θ of the turning motor 41 b Angle θ with pinion p By using this correlation, the rotation angle θ of the turning motor 41 can be b Get the pinion angle θ p In addition, the pinion shaft 44 is meshed with the turning shaft 14. Therefore, at the pinion angle θ p There is also a correlation between the amount of movement of the turning axis 14. That is, the pinion angle θ p is the turning angle θ of the turning wheel 16 w value.

[0046] The target pinion angle calculator 62 calculates the steering angle θ based on the steering angle θ calculated by the steering angle calculator 51. s The target pinion angle θ is calculated based on the vehicle speed V detected by the vehicle speed sensor 501. p * The target pinion angle calculator 62 sets the turning angle θ according to the vehicle speed V, for example. w and steering angle θ s The target pinion angle θ is calculated based on the steering angle ratio. p * The target pinion angle calculator 62 calculates the target pinion angle θ p * , so that as the vehicle speed V slows down, the turning angle θ w Relative to the steering angle θ s becomes larger, and as the vehicle speed V becomes faster, the turning angle θ w Relative to the steering angle θ s Get bigger.

[0047] In addition, the target pinion angle calculator 62 may calculate the target pinion angle θ according to product specifications and the like. p * Set to the steering angle θ s In this case, the steering angle θ s and the turning angle θ w The steering angle ratio of the ratio is "1:1".

[0048] 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 the pinion angle calculator 61 p The pinion angle feedback controller 63 controls the pinion angle θ p The feedback control is used to calculate the pinion angle command value T p *, so that the actual pinion angle θ p Following target pinion angle θ p *.

[0049] The limit value controller 64 calculates the limit value I for limiting the amount of current supplied to the turning motor 41 according to, for example, the heating state of the turning motor 41. lim Based on the premise of preventing the turning motor 41 from overheating, the limit value I lim The limit value controller 64 is based on the temperature T of the turning motor 41 detected by the temperature sensor 62a provided near the power feeding path of the turning motor 41. mThe comparison result with the temperature threshold is used to calculate the limit value I lim .

[0050] When the temperature T of the turning motor 41 m When the temperature threshold is not exceeded, the limit value controller 64 calculates the limit value I based on the maximum current value that can be applied without overheating the turning motor 41. lim , the limit value I lim The absolute value of is large enough not to limit the current that the power controller 65 attempts to supply to the turning motor 41. On the other hand, when the temperature T of the turning motor 41 m When the temperature threshold is exceeded, the limit value controller 64 calculates the following limit value I lim , the limit value I lim The absolute value of is less than the maximum current value that can be applied to the turning motor 41 without overheating the turning motor 41. The limit value controller 64 calculates the limit value I lim , as the temperature T of the turning motor 41 m The higher the limit value I lim The smaller the absolute value of .

[0051] In addition, the limit value I lim It can be a fixed value. As a limit value of the fixed value I lim is stored in the storage device of the control device 50. In the case of adopting the above configuration, when the temperature T of the turning motor 41 m When the temperature threshold is exceeded, the limit value controller 64 can set the limit value I as a fixed value. lim Set to the temperature T of the turning motor 41 m The limit value I for the current of the turning motor 41 is irrelevant. lim In addition, when the temperature T of the turning motor 41 is m When the temperature threshold is not exceeded, the limit value controller 64 may not set the limit value I for the current amount of the turning motor 41. lim .

[0052] The limit value controller 64 is based on the temperature T of the turning motor 41. m The value of the flag F is set to determine whether the temperature threshold is exceeded, that is, whether the current of the turning motor 41 must be limited. m When the temperature threshold is exceeded, that is, when the current of the turning motor 41 must be limited, the limit value controller 64 sets the value of the flag F to "1". m When the temperature threshold value is not exceeded, that is, when the current amount of the turning motor 41 does not need to be limited, the limit value controller 64 sets the value of the flag F to "0".

[0053] The controller 65 is powered on according to the pinion angle command value T p * Power is supplied to the turning motor 41. Specifically, the energization controller 65 supplies power to the turning motor 41 based on the pinion angle command value T p * The current command value for the turning motor 41 is calculated. In addition, the energization controller 65 detects the actual current I generated in the power feeding path of the turning motor 41 through the current sensor 66 provided in the power feeding path. b The value of current I b The value of is the actual current value supplied to the turning motor 41. Then, the energization controller 65 obtains the current command value and the actual current I b and controls the power feed to the turning motor 41 to eliminate the deviation (for current I b In this way, the turning motor 41 rotates according to the pinion angle command value T p * angle.

[0054] When the limit value controller 64 calculates the limit value I lim When the power controller 65 is turned on, the power controller 65 is turned on according to the limit value I lim The current amount supplied to the turning motor 41 is limited. The energization controller 65 compares the absolute value of the current to be supplied to the turning motor 41 with the limit value I lim When the absolute value of the current to be supplied to the turning motor 41 is greater than the limit value I lim When the energization controller 65 limits the absolute value of the current to be supplied to the turning motor 41 to the limit value I lim In this way, the torque generated by the turning motor 41 is limited to the value according to the limit value I lim On the other hand, when the absolute value of the current supplied to the turning motor 41 is equal to or less than the limit value I lim When the power controller 65 is on, the current I b The original current calculated by the feedback control of φ is supplied as it is to the turning motor 41. The torque generated by the turning motor 41 is not limited.

[0055] Next, the steering reaction force command value calculator 52 will be described in detail. 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 .

[0056] The target steering reaction force calculator 71 is based on the steering torque T h Calculate the target steering reaction force T1 using the vehicle speed V * Target steering reaction force T1 *The target steering reaction force calculator 71 calculates the target value of the torque generated by the reaction force motor 31 in the direction opposite to the direction of operation of the steering wheel 11. h The larger the absolute value of and the slower the vehicle speed V, the larger the absolute value of the target steering reaction force T1 * .

[0057] The axial force calculator 72 is based on the pinion angle θ p , the current I of the turning motor 41 b The axial force acting on the turning axis 14 is calculated by using the value of and the vehicle speed V, and the torque conversion value T2 is calculated by converting the calculated axial force into the torque of the steering wheel 11 or the steering shaft 12. * The axial force calculator 72 will be described in detail later.

[0058] The subtractor 73 calculates the target steering reaction force T1 from the target steering reaction force calculator 71. * Subtract the torque conversion value T2 calculated by the axial force calculator 72 * To calculate the steering reaction force command value T * .

[0059] Next, the axial force calculator 72 will be described in detail. Figure 3 As shown, the axial force calculator 72 includes an angular axial force calculator 81A, a current axial force calculator 81B, an axial force distribution calculator 81C, and a converter 81D.

[0060] Angular axial force calculator 81A is based on the pinion angle θ p The angular axial force AF1 is calculated, which is an ideal value of the axial force acting on the turning axis 14. The angular axial force calculator 81A calculates the angular axial force AF1 by using, for example, an angular axial force map stored in the storage device of the control device 50. The angular axial force map is a map in which the horizontal axis represents the pinion angle θ. p , the vertical axis represents the angular axial force AF1, the pinion angle θ p The relationship between the angular axial force AF1 and the vehicle speed V is defined. The angular axial force map has the following characteristics. That is, as the pinion angle θ p As the absolute value of the angular axial force AF1 increases and the vehicle speed V slows down, the absolute value of the angular axial force AF1 is set to be larger. The absolute value of the angular axial force AF1 increases with the pinion angle θ p The angular axial force AF1 is set to increase linearly with the increase of the absolute value of the pinion angle θ. p The angular axial force AF1 is an axial force that does not reflect the road surface conditions or the forces acting on the turning axis 14 .

[0061] The current axial force calculator 81B is based on the current I b The current axial force AF2 acting on the turning shaft 14 is calculated from the value of b The value of is due to the fact that disturbances caused by road conditions such as road friction resistance act on the turning wheel 16, and is calculated based on the target pinion angle θ. p * and the actual pinion angle θ p That is, the current I of the turning motor 41 changes b The actual road condition acting on the turning wheel 16 is reflected in the value of b The axial force reflecting the influence of the road surface condition is calculated by multiplying the current I of the turning motor 41 by the gain which is a coefficient according to the vehicle speed V. b The current axial force AF2 is obtained by using the value of . The current axial force AF2 is an axial force that reflects the road surface condition or the force acting on the turning shaft 14 through the turning wheel 16.

[0062] The axial force distribution calculator 81C sets the distribution ratios of the angular axial force AF1 and the current axial force AF2, respectively, according to various vehicle state variables. The vehicle state variables are variables reflecting vehicle conditions including vehicle behavior, steering conditions, or road conditions, and examples thereof may include yaw rate, lateral acceleration, steering angle θ, and the like. s , pinion angle θ p , as well as the vehicle speed V, steering speed and pinion angular velocity. s Differentiate to get the steering speed. p Differentiate to obtain the pinion angular velocity.

[0063] The axial force distribution calculator 81C adds the values ​​obtained by multiplying the angular axial force AF1 and the current axial force AF2 by the respectively set distribution ratios, thereby calculating the final axial force AF3 to be reflected in the steering reaction force command value T * The final axial force AF3 is expressed by the following equation (1).

[0064] AF3=AF1·DR1+AF2·DR2…(1)

[0065] Note that "DR1" is the distribution ratio of the angular axial force AF1, and "DR2" is the distribution ratio of the current axial force AF2. Distribution ratio DR1 indicates the extent to which the angular axial force AF1 is reflected in the final axial force AF3. Distribution ratio DR2 indicates the extent to which the current axial force AF2 is reflected in the final axial force AF3.

[0066] The axial force distribution calculator 81C sets each of the two distribution ratios DR1 and DR2 based on various vehicle state variables reflecting the vehicle's driving state or steering condition. Furthermore, the axial force distribution calculator 81C may set the values ​​of the two distribution ratios DR1 and DR2 within a range of "0 (0%)" to "1 (100%)," for example, in increments of "0.1," based on product specifications. Note that the axial force distribution calculator 81C sets each of the two distribution ratios DR1 and DR2 so that the sum of the values ​​of the two distribution ratios DR1 and DR2 is "1."

[0067] The converter 81D calculates the torque conversion value T2 by converting the final axial force AF3 calculated by the axial force distribution calculator 81C into the torque of the steering wheel 11. * According to the steering device 10 configured in this manner, the torque conversion value T2 obtained by converting the final axial force AF3 calculated by the axial force calculator 72 into the torque * Reflected in the steering reaction force command value T * In this way, a steering reaction force according to the vehicle behavior or road surface condition can be applied to the steering wheel 11. Therefore, the driver can grasp the vehicle behavior or road surface condition by feeling the steering reaction force as a response through the steering wheel 11.

[0068] However, the steering device 10 may encounter the following limitations. Specifically, when the current flowing to the turning motor 41 is limited due to the overheat protection function of the turning motor 41, the current axial force AF2, and thus the torque generated by the turning motor 41, may decrease due to the current limitation. Consequently, for example, even when the steering reaction force must be further increased as a signal to the driver, the initially requested steering reaction force may not be ensured.

[0069] Therefore, the following configuration can be adopted as the axial force calculator 72. Figure 3 As shown, the axial force calculator 72 includes a distribution ratio calculator 81E. The distribution ratio calculator 81E receives the value of a flag F set by the limit value controller 64. When the value of flag F is "1," the distribution ratio calculator 81E sets the distribution ratios DR1 and DR2 used when limiting the current of the turning motor 41. The distribution ratios DR1 and DR2 used during current limiting take precedence over the distribution ratios DR1 and DR2 calculated by the axial force distribution calculator 81C.

[0070] When the value of flag F is "1," meaning the current flow to the turning motor 41 must be limited, the distribution ratio calculator 81E sets the distribution ratio DR1 of the angular axial force AF1 to the final axial force AF3 to "1 (100%)" and sets the distribution ratio DR2 of the current axial force AF2 to the final axial force AF3 to "0 (0%)." Furthermore, when the value of flag F is "0," meaning the current flow to the turning motor 41 does not need to be limited, the distribution ratio calculator 81E does not set the distribution ratios DR1 and DR2 used for current limitation.

[0071] When the distribution ratios DR1 and DR2 used in current limitation are set by the distribution ratio calculator 81E, the axial force distribution calculator 81C preferentially uses the distribution ratios DR1 and DR2 instead of the distribution ratios DR1 and DR2 calculated by the axial force distribution calculator 81C. Here, the value of the distribution ratio DR1 used by the angular axial force AF1 in current limitation is set to "1 (100%)", while the value of the distribution ratio DR2 used by the current axial force AF2 in current limitation is set to "0 (0%)". Therefore, it can be seen from the above formula (1) that the value of the final axial force AF3 is the same as the value of the angular axial force AF1 calculated by the angular axial force calculator 81A. That is, the angular axial force AF1 calculated by the angular axial force calculator 81A is used as the final axial force AF3 as it is to control the reaction force motor 31.

[0072] In addition, depending on product specifications, etc., the axial force distribution calculator 81C may have the function of a distribution ratio calculator 81E. In this case, as the axial force calculator 72, a configuration in which the distribution ratio calculator 81E is omitted may be adopted. The axial force distribution calculator 81C receives the value of the flag F set by the limit value controller 64. When the value of the flag F is "1", the axial force distribution calculator 81C sets the values ​​of the distribution ratios DR1 and DR2 used when the current of the turning motor 41 is limited. The distribution ratios DR1 and DR2 used when the current is limited are used in priority over the distribution ratios DR1 and DR2 calculated based on various vehicle state variables reflecting the vehicle behavior, steering conditions, or road conditions.

[0073] Next, the operation of the first embodiment will be described. In a normal state where the current of the turning motor 41 is not limited, the control device 50 calculates a final axial force AF3 by adding the angular axial force AF1 and the current axial force AF2 at a distribution ratio set according to the vehicle behavior, the turning condition, or the road surface condition, and controls the reaction force motor 31 using the calculated final axial force AF3. The angular axial force AF1 is based on the pinion angle θ. p The ideal axial force, which does not reflect the road conditions. The current axial force AF2 is based on the current I of the turning motor 41. bThe axial force of the value of is , which reflects the road surface condition. Therefore, the reaction force motor 31 generates a steering reaction force based on the vehicle's behavior, steering condition, or road surface condition. Therefore, the driver can understand the vehicle's behavior, steering condition, or road surface condition by feeling the steering reaction force in response through the steering wheel 11.

[0074] Next, when limiting the current of the turning motor 41 from the standpoint of overheat protection of the turning motor 41, the control device 50 controls the turning motor 41 by using the limit value I set by the limit value controller 64. lim To limit the amount of current supplied to the turning motor 41. b The value is limited to at least the limit value I lim , the temperature rise of the turning motor 41 is suppressed, and the current I b As the current decreases, the temperature of the turning motor 41 gradually decreases, eventually reaching a temperature lower than the temperature threshold. As a result, the turning motor 41 is prevented from overheating.

[0075] Furthermore, when limiting the current of the turning motor 41 from the standpoint of overheat protection of the turning motor 41, the control device 50 controls the steering reaction force command value T * The angular axial force AF1 is only reflected in the angular axial force AF1 and the current axial force AF2. The angular axial force AF1 is not affected by the current I of the turning motor 41. b Specifically, the control device 50 sets the distribution ratio DR1 of the angular axial force AF1 to the final axial force AF3 to "1 (100%)", and sets the distribution ratio DR2 of the current axial force AF2 to the final axial force AF3 to "0 (0%)". b The change in the current axial force AF2 is not reflected in the steering reaction force command value T * Therefore, the torque generated by the reaction motor 31 is not affected by the current I of the turning motor 41. b Therefore, the current I of the turning motor 41 b When restricted, the steering reaction force applied to the steering wheel 11 is not restricted.

[0076] Even if the current I of the turning motor 41 b Under the condition of being restricted, by adjusting the steering reaction force command value T * The angular axial force AF1 and the current axial force AF2 are only reflected in the pinion angle θ p The angular axial force AF1, and the pinion angle θ p The corresponding steering reaction force is applied to the steering wheel 11. For example, as the pinion angle θ pTherefore, in the case where the steering reaction force must be increased as information for the driver, for example, when the steering wheel 11 is turned more, the absolute value of the angular axial force AF1 is set larger according to the pinion angle θ. p An appropriate steering reaction force is applied to the steering wheel 11 as information for the driver.

[0077] Therefore, according to the first embodiment, the following effects can be obtained. b In certain cases where it must be limited, the current I of the turning motor 41 is not used. b The current axial force AF2 is calculated, and the angular axial force AF1 which is not affected by the current limitation of the turning motor 41 is calculated as the final axial force AF3. The final axial force AF3 is reflected in the steering reaction force command value T * Therefore, even when the current of the turning motor 41 is limited, the steering reaction force as information for the driver can be ensured. b Steering feel and current I of the steering motor 41 during normal operation of the system without restriction b Both can be compatible with steering feel during protection operation of the limited system.

[0078] When the current I of the turning motor 41 appears b In a specific case where the current axial force AF2 must be limited, the distribution ratio calculator 81E sets the distribution ratio of the current axial force AF2 to the final axial force AF3 to 0%, and sets the distribution ratio of the angular axial force AF1 to the final axial force AF3 to 100%. Therefore, when the current I b In the specific case where the current is already limited, the final axial force AF3 is calculated by using the distribution ratios DR1 and DR2 used when the current is limited, which are calculated by the distribution ratio calculator 81E, so that the steering reaction force as information for the driver can be ensured even when the current of the turning motor 41 is limited.

[0079] Second embodiment

[0080] Next, a second embodiment in which the steering control device is implemented as a steer-by-wire type steering device will be described. Figure 1 and Figure 2 The present embodiment is different from the first embodiment in the configuration of the axial force calculator 72 .

[0081] like Figure 4As shown, the axial force calculator 72 includes an angular axial force calculator 81A, a current axial force calculator 81B, a converter 81D, and a switch 81F. The switch 81F receives as data input the angular axial force AF1 calculated by the angular axial force calculator 81A and the current axial force AF2 calculated by the current axial force calculator 81B. Furthermore, the switch 81F receives as control input the value of a flag F set by the limit value controller 64. Based on the value of the flag F, the switch 81F selects either the angular axial force AF1 calculated by the angular axial force calculator 81A or the current axial force AF2 calculated by the current axial force calculator 81B as the final axial force AF3, which is the final axial force used to control the reaction force motor 31.

[0082] When the value of flag F is "0", switch 81F selects the current axial force AF2 calculated by current axial force calculator 81B as final axial force AF3. When the value of flag F is "1", switch 81F selects the angular axial force AF1 calculated by angular axial force calculator 81A as final axial force AF3.

[0083] Next, the operation of the second embodiment will be described. In a normal state where the current of the turning motor 41 is not limited, the control device 50 selects the current I of the turning motor 41 from the angular axial force AF1 and the current axial force AF2. b The current axial force AF2 is used as the final axial force AF3 and the reaction force motor 31 is controlled using the selected final axial force AF3. The current axial force AF2 is the current I based on the turning motor 41 that reflects the road surface condition. b Therefore, the reaction force motor 31 generates a steering reaction force according to the vehicle behavior or road conditions. Therefore, the driver can understand the vehicle behavior or road conditions by feeling the steering reaction force as a response through the steering wheel 11.

[0084] In addition, when limiting the current of the turning motor 41 from the standpoint of overheat protection of the turning motor 41, the control device 50 selects the current I of the turning motor 41 from the angle axial force AF1 and the current axial force AF2. b The angular axial force AF1 is affected as the final axial force AF3. b The change in the current axial force AF2 is not reflected in the steering reaction force command value T * Therefore, the torque generated by the reaction motor 31 is not affected by the current I of the turning motor 41. b Therefore, the current I of the turning motor 41 b When the current I of the turning motor 41 is limited, the steering reaction force applied to the steering wheel 11 is not limited. bWhen limited, according to the pinion angle θ p An appropriate steering reaction force is also applied to the steering wheel 11 as information for the driver.

[0085] Therefore, according to the second embodiment, in addition to the same effects as those of the first embodiment, the following effects can be obtained. b Under the condition of limitation, the steering reaction force command value T can be changed only by operating the switch 81F. * The axial force in the current axial force AF2 is switched to the angular axial force AF1. Therefore, the calculation load of the control device 50 can be reduced.

[0086] Third embodiment

[0087] Next, a third embodiment in which the steering control device is implemented as a steer-by-wire type steering device will be described. Figures 1 to 3 The same configuration as that of the first embodiment shown can be applied to the second embodiment.

[0088] In the first embodiment, the case where the current of the turning motor 41 must be limited is exemplified by the case where the turning motor 41 is close to being overheated, but the case may also include a case where the power supply voltage of the vehicle is reduced.

[0089] The limit value controller 64 is based on the above Figure 2 The double-dashed line in FIG. 1 shows the voltage V of a DC power source such as a battery detected by the voltage sensor 502. b , calculate the limit value I for limiting the amount of current supplied to the turning motor 41 lim . From the suppression DC power supply voltage V b Starting from the foothold of the decline, the limit value I lim is set as the upper limit value of the current amount supplied to the turning motor 41. When the voltage V b When the voltage is equal to or less than the voltage threshold, the limit value controller 64 calculates the limit value I according to the voltage value at this time. lim The voltage threshold is set with reference to the lower limit value of the guaranteed operation voltage range that guarantees the operation of the turning motor 41 .

[0090] In addition, the limit value controller 64 is based on the voltage V b Is it equal to or less than the voltage threshold, that is, the voltage V of the DC power supply? b Whether to reduce the value of flag F. When the voltage V b When the voltage V of the DC power supply is equal to or less than the voltage threshold, bWhen the voltage V b When the voltage V b When not decreasing, the limit value controller 64 sets the value of the flag F to "0".

[0091] Therefore, according to the third embodiment, the following effects can be obtained. By limiting the current I supplied to the turning motor 41 when the power supply voltage of the vehicle decreases, b , further reduction of the power supply voltage can be suppressed. In addition, even if the current I of the turning motor 41 is reduced due to the reduction of the power supply voltage of the vehicle, b Instead of limiting the current of the turning motor 41 , it is also possible to apply an appropriate steering reaction force as information for the driver by controlling the driving of the turning motor 41 using the angular axial force AF1 that is not affected by the current limitation of the turning motor 41 .

[0092] Fourth embodiment

[0093] Next, a fourth embodiment in which the steering control device is implemented as a steer-by-wire type steering device will be described. Figures 1 to 3 The same configuration as the first embodiment shown.

[0094] In the first embodiment, when the current I of the turning motor 41 occurs b When restrictions are necessary, the distribution ratio calculator 81E sets the distribution ratio DR1 of the angular axial force AF1 to "1 (100%)" and sets the distribution ratio DR2 of the current axial force AF2 to "0 (0%)", but the present invention is not limited thereto.

[0095] For example, when the current I of the turning motor 41 occurs b When restrictions are necessary, the distribution ratio DR1 of the angular axial force AF1 and the distribution ratio DR2 of the current axial force AF2 can be set as shown in the following relational expression (2) or relational expression (3). Note that the two distribution ratios DR1 and DR2 are set so that the sum of the two distribution ratios is "1 (100%)". In addition, the two distribution ratios DR1 and DR2 are set to appropriate values ​​according to product specifications, etc.

[0096] DR1:DR2=0.8(80%):0.2(20%)…(2)

[0097] DR1:DR2=0.9(90%):0.1(10%)…(3)

[0098] As described above, the distribution ratio DR1 of the angular axial force AF1 does not necessarily have to be "1 (100%)".b In certain situations where restrictions must be imposed, the two distribution ratios DR1 and DR2 can be set to values ​​where the degree of reflection of the current axial force AF2 in the final axial force AF3 decreases, while the degree of reflection of the angular axial force AF1 in the final axial force AF3 increases. In other words, it is sufficient for the angular axial force AF1 to become more dominant in the final axial force AF3.

[0099] Therefore, according to the fourth embodiment, the following effects can be obtained. b In certain situations where the current axial force AF2 must be limited, the degree of reflection of the current axial force AF2 in the final axial force AF3 decreases, while the degree of reflection of the angular axial force AF1 in the final axial force AF3 increases. That is, since the angular axial force AF1 becomes more dominant in the final axial force AF3, even if the current I b Even when limited, the steering reaction force can be ensured as information for the driver.

[0100] Fifth embodiment

[0101] Next, a fifth embodiment will be described in which the steering control device is implemented as a steer-by-wire type steering device. Figures 1 to 3 The same configuration as the first embodiment shown.

[0102] Similar to the third embodiment described above, when assuming various situations in which the current of the turning motor 41 must be limited, the two distribution ratios DR1 and DR2 may be different depending on the situation.

[0103] In addition to setting the value of flag F, the limit value controller 64 generates unique identification information for each situation in which the current of the turning motor 41 must be limited. The distribution ratio calculator 81E receives the value of flag F and the identification information. When the value of flag F is "1," the distribution ratio calculator 81E sets the value of the distribution ratio DR1 of the angular axial force AF1 relative to the final axial force AF3 and the value of the distribution ratio DR2 of the current axial force AF2 relative to the final axial force AF3 based on the identification information, namely, the situation in which the current of the turning motor 41 must be limited. In this case, the value of the distribution ratio DR1 of the angular axial force AF1 and the value of the distribution ratio DR2 of the current axial force AF2 are set to different values ​​depending on the situation in which the current of the turning motor 41 must be limited. Note that the two distribution ratios DR1 and DR2 are set so that the sum of the two distribution ratios is "1 (100%)." Furthermore, the two distribution ratios DR1 and DR2 are set to appropriate values ​​based on product specifications, etc.

[0104] For example, when the turning motor 41 is in an overheated state, the value of the distribution ratio DR1 of the angular axial force AF1 and the value of the distribution ratio DR2 of the current axial force AF2 are set as represented by the following relational expression (4).

[0105] DR1:DR2=1(100%):0(0%)…(4)

[0106] In addition, when the DC power supply voltage V b When decreasing, the value of the distribution ratio DR1 of the angular axial force AF1 and the value of the distribution ratio DR2 of the current axial force AF2 are set to be represented by the following relational expression (5) or (6).

[0107] DR1:DR2=0.8(80%):0.2(20%)…(5)

[0108] DR1:DR2=0.9(90%):0.1(10%)…(6)

[0109] Therefore, according to the fifth embodiment, the following effects can be obtained.

[0110] When the current I of the turning motor 41 appears b In certain cases where the current I of the turning motor 41 must be limited, b The two distribution ratios DR1 and DR2 must be set to the values ​​that are limited. b Whatever the case, the angular axial force AF1 becomes more dominant in the final axial force AF3. Therefore, when the current I b In certain cases where the current I of the turning motor 41 must be limited, b The situations that must be limited ensure the steering reaction force as information for the driver.

[0111] Sixth embodiment

[0112] Next, a sixth embodiment will be described in which the steering control device is implemented as a steer-by-wire type steering device. Figures 1 to 3 This embodiment can be applied to the third to fifth embodiments.

[0113] According to the product specifications, the following configuration can be adopted for the axial force calculator 72. That is, Figure 5 As shown, the axial force calculator 72 has a lateral G axial force calculator 81G in addition to the angular axial force calculator 81A, the current axial force calculator 81B, the axial force distribution calculator 81C, the converter 81D, and the distribution ratio calculator 81E.

[0114] The lateral G axial force calculator 81G calculates the lateral G axial force AF4, which is the axial force acting on the turning axis 14, based on the lateral acceleration LA detected by the lateral acceleration sensor 503 provided in the vehicle. For example, the lateral G axial force AF4 is obtained by multiplying the lateral acceleration LA by a gain, which is a coefficient based on the vehicle speed V. Since the behavior of the vehicle is reflected in the lateral acceleration LA, the behavior of the vehicle is also reflected in the lateral G axial force AF4 calculated based on the lateral acceleration LA. Since the lateral G axial force AF4 is calculated based on the lateral acceleration LA, the lateral G axial force AF4 is not easily affected by the current I of the turning motor 41. b the impact of changes.

[0115] The axial force distribution calculator 81C calculates the final axial force AF3 by adding the angular axial force AF1, the current axial force AF2, and the lateral G axial force AF4 at a predetermined distribution ratio set according to various vehicle state variables reflecting the driving state or steering condition of the vehicle. Examples of vehicle state variables include vehicle speed V, steering angle θ, s and pinion angle θ p By reflecting the final axial force AF3 in the steering reaction force command value T * In this case, a more appropriate steering reaction force can be applied to the steering wheel 11 according to the vehicle behavior. In addition, the final axial force AF3 at this time is expressed by the following expression (7).

[0116] AF3=AF1·DR1+AF2·DR2+AF4·DR4…(7)

[0117] Note that "DR1" is the distribution ratio of the angular axial force AF1, "DR2" is the distribution ratio of the current axial force AF2, and "DR4" is the distribution ratio of the lateral G axial force AF4.

[0118] When the value of the flag F is "1", the distribution ratio calculator 81E sets the values ​​of the distribution ratios DR1, DR2 and DR4 used in the current limitation for the angular axial force AF1, the current axial force AF2 and the lateral G axial force AF4. * The distribution ratios DR1, DR2, and DR4 used during current limiting are set to appropriate values ​​based on product specifications, etc., taking into account the influence of the current on the steering reaction force and the subsequent influence on the steering reaction force. Furthermore, the distribution ratios DR1, DR2, and DR4 used during current limiting take precedence over the distribution ratios DR1, DR2, and DR4 set by the axial force distribution calculator 81C.

[0119] When the value of flag F is "1", the distribution ratio calculator 81E sets the values ​​of the distribution ratios DR1, DR2, and DR4 used during current limiting, so that the degree of reflection of the current axial force AF2 in the final axial force AF3 is reduced, while the total degree of reflection of the angular axial force AF1 and the lateral G axial force AF4 in the final axial force AF3 is increased.

[0120] When the value of the flag F is "1", the distribution ratio calculator 81E may, for example, set the value of the distribution ratio DR2 of the current axial force AF2 to "0 (0%)", set the value of the distribution ratio DR1 of the angular axial force AF1 to "0.5 (50%)", and set the value of the distribution ratio DR4 of the lateral G axial force AF4 to "0.5 (50%)". In addition, when the value of the flag F is "1", the distribution ratio calculator 81E may, for example, set the value of each of the distribution ratio DR2 of the current axial force AF2 and the value of the distribution ratio DR1 of the angular axial force AF1 to "0", while setting the value of the distribution ratio DR4 of the lateral G axial force AF4 to "1".

[0121] In this way, the degree of reflection of the current axial force AF2 in the final axial force AF3 is reduced, while the total degree of reflection of the angular axial force AF1 and the lateral G axial force AF4 in the final axial force AF3 is increased. Therefore, the current limit of the turning motor 41 has an effect on the steering reaction force command value T * The influence of the steering reaction force is suppressed.

[0122] Furthermore, as in the fourth embodiment described above, even when the value of the flag F is "1," the distribution ratio calculator 81E may not set the value of the distribution ratio DR2 of the current axial force AF2 to "0 (0%)." When the value of the flag F is "1," the distribution ratio calculator 81E may, for example, set the value of the distribution ratio DR2 of the current axial force AF2 to "0.1 (10%)," set the value of the distribution ratio DR1 of the angular axial force AF1 to "0.6 (60%)," and set the value of the distribution ratio DR4 of the lateral G axial force AF4 to "0.3 (30%)."

[0123] Even in this way, the degree of reflection of the current axial force AF2 in the final axial force AF3 decreases, while the total degree of reflection of the angular axial force AF1 and the lateral G axial force AF4 in the final axial force AF3 increases. Therefore, the current limit of the turning motor 41 has an effect on the steering reaction force command value T * The influence of the steering reaction force is suppressed.

[0124] Therefore, according to the sixth embodiment, the following effects can be obtained. When the current I bIn certain cases where the current I of the turning motor 41 must be limited, b The calculated current axial force AF2 is reflected less in the final axial force AF3, and is affected by the current I b The total reflection degree of the angular axial force AF1 and the lateral G axial force AF4, which are less affected by the change of the angular axial force AF1, in the final axial force AF3 increases. Therefore, the influence of the current limit of the turning motor 41 on the steering reaction force command value T can be suppressed. * Therefore, even when the current of the turning motor 41 is limited, the steering reaction force as information for the driver can be ensured.

[0125] In addition, if Figure 5 As indicated by the reference numerals in square brackets, a yaw rate axial force calculator 81H may be provided in place of the lateral G axial force calculator 81G. The yaw rate axial force calculator 81H calculates the yaw rate axial force AF5, an axial force acting on the turning axis 14, based on the yaw rate YR detected by the yaw rate sensor 504 provided in the vehicle. The yaw rate axial force AF5 is obtained by multiplying the yaw rate differential value, which is obtained by differentiating the yaw rate YR, by a vehicle speed gain, which is a coefficient based on the vehicle speed V. As the vehicle speed V increases, the vehicle speed gain is set to a larger value. Since the vehicle's behavior is reflected in the yaw rate YR, the vehicle's behavior is also reflected in the yaw rate axial force AF5 calculated based on the yaw rate YR. Furthermore, since the yaw rate axial force AF5 is calculated based on the yaw rate YR, it is less susceptible to the current limitation of the turning motor 41. Therefore, even when the yaw rate axial force calculator 81H is provided instead of the lateral G axial force calculator 81G, the same effect as when the lateral G axial force calculator 81G is provided can be obtained.

[0126] Furthermore, depending on product specifications, etc., a configuration in which the axial force calculator 72 is omitted from the angular axial force calculator 81A may be employed. In the case where the above configuration is employed, when the current I b In specific situations where current limitation is necessary, the distribution ratio calculator 81E calculates the distribution ratios DR2 and DR4 used during current limitation so that the current axial force AF2 is less reflected in the final axial force AF3, while the lateral G axial force AF4 is more reflected in the final axial force AF3. This reduces the effect of current limitation on the steering reaction force of the turning motor 41.

[0127] Seventh embodiment

[0128] Next, a seventh embodiment will be described in which the steering control device is implemented as a steer-by-wire type steering device. This embodiment basically has the same configuration as the second embodiment described above. This embodiment differs from the first embodiment in the configuration of the axial force calculator 72.

[0129] like Figure 6 As shown, the axial force calculator 72 has the same configuration as that of the second embodiment, namely, an angular axial force calculator 81A, a current axial force calculator 81B, a converter 81D and a switch 81F, and further has a lateral G axial force calculator 81G.

[0130] When the value of flag F is "0," switch 81F selects the current axial force AF2 calculated by current axial force calculator 81B as final axial force AF3. When the value of flag F is "1," switch 81F selects the angular axial force AF1 calculated by angular axial force calculator 81A or the lateral G axial force AF4 calculated by lateral G axial force calculator 81G as final axial force AF3. Note that the axial force selected when flag F is "1" is determined by the product specifications.

[0131] Therefore, according to the seventh embodiment, the following effects can be obtained. b In certain cases where it must be limited, the current I of the turning motor 41 is not used. b The calculated current axial force AF2. That is, the angular axial force AF1 or the lateral G axial force AF4 not affected by the current limitation of the turning motor 41 is calculated as the final axial force AF3, which is reflected in the steering reaction force command value T * Therefore, even when the current of the turning motor 41 is limited, the steering reaction force as information for the driver can be ensured.

[0132] In addition, when the current I b In special cases where restrictions must be imposed, the steering reaction force command value T can be set to * The reflected axial force is switched from the current axial force AF2 to the angular axial force AF1 or the lateral G axial force AF4. Therefore, the calculation load of the control device 50 can be reduced.

[0133] Furthermore, depending on product specifications, etc., a configuration in which the axial force calculator 72 is omitted from the angular axial force calculator 81A may be employed. In the case where the above configuration is employed, when the current I bIn specific situations where limitation is necessary, the lateral G axial force AF4 is calculated as the final axial force AF3. The lateral G axial force AF4 is not easily affected by the current limitation of the turning motor 41. Therefore, even when the current of the turning motor 41 is limited, a steering reaction force that serves as information for the driver can be ensured.

[0134] like Figure 6 As shown in the reference numerals in the brackets, a yaw rate axial force calculator 81H may be provided instead of the lateral G axial force calculator 81G. b In specific situations where limitation is necessary, the angular axial force AF1 or the yaw rate axial force AF5 is calculated as the final axial force AF3. The yaw rate axial force AF5 is not easily affected by the current limitation of the turning motor 41. Therefore, even when the current of the turning motor 41 is limited, a steering reaction force can be ensured as information for the driver.

[0135] Eighth embodiment

[0136] Next, an eighth embodiment in which the steering control device is implemented as a steer-by-wire type steering device will be described. Figures 1 to 3 The same configuration as that of the first embodiment shown in FIG. Furthermore, in this embodiment, as in the above-described third embodiment, various situations are assumed in which the current of the turning motor 41 must be limited.

[0137] The reaction force controller 50a and the turning controller 50b of the control device 50 are provided as separate electronic control units (ECUs) independent of each other and exchange information with each other via an in-vehicle network such as a controller area network (CAN).

[0138] The limit value controller 64 detects the temperature T of the turning motor 41 through the temperature sensor 62a. m The limit value controller 64 sets the temperature T of the turning motor 41 to m The heating state of the turning motor 41 is determined by comparing the heating state with a plurality of temperature thresholds. The heating state of the turning motor 41 includes a normal heating state in which heat is not generated enough to limit the current of the turning motor 41, a slightly overheated state, a moderately overheated state, and a severely overheated state. The limit value controller 64 calculates the limit value I whose absolute value becomes smaller as the degree of overheating of the turning motor 41 increases. lim .

[0139] In addition, the limit value controller 64 detects the voltage V of the DC power supply through the voltage sensor 502. b The limit value controller 64 sets the voltage V bThe voltage state of the DC power supply is determined by comparing it with a plurality of voltage thresholds. The voltage state of the DC power supply includes a normal voltage state where the voltage is not reduced enough to limit the current of the turning motor 41, a slightly reduced voltage state, a moderately reduced voltage state, and a severely reduced voltage state. The limit value controller 64 calculates the limit value I whose absolute value becomes smaller as the degree of reduction in the DC power supply voltage increases. lim .

[0140] Rather than setting the value of flag F, which indicates whether the current flow to the turning motor 41 must be limited, the limit value controller 64 performs the following processing. Specifically, the limit value controller 64 encodes the state of the steering system 10 based on a code table stored in the storage device of the control device 50. Encoding is the process of expressing the state of the steering system 10 using codes as symbols. The state of the steering system 10 includes the heating state of the turning motor 41 and the voltage state of the DC power supply. An example of the correspondence between the state of the steering system 10 and the codes is shown below.

[0141] -Code "0": Normal state where the current of the turning motor 41 is not limited

[0142] -Code "1A": Slight overheating of the turning motor 41

[0143] -Code "1B": Moderate overheating of the turning motor 41

[0144] -Code "1C": Severe overheating of the turning motor 41

[0145] -Code "2A": Slightly reduced voltage state of DC power supply

[0146] -Code "2B": Moderate voltage reduction state of DC power supply

[0147] -Code "2C": Severely reduced voltage state of DC power supply

[0148] The turning controller 50b transmits a code set by the limit value controller 64 to the reaction force controller 50a via the in-vehicle network. The reaction force controller 50a receives the code via the in-vehicle network and executes reaction force control based on the received code. For example, the reaction force controller 50a changes the distribution ratio DR1 of the angular axial force AF1 and the distribution ratio DR2 of the current axial force AF2 according to the code as part of the reaction force control. For example, the distribution ratio calculator 81E gradually changes the values ​​of the two distribution ratios DR1 and DR2 based on the degree to which the current of the turning motor 41 needs to be limited, as determined from the code.

[0149] When the turning motor 41 is in an overheated state, as the overheating condition worsens in the order of "mild," "moderate," and "severe," the distribution ratio calculator 81E sets the distribution ratio DR1 of the angular axial force AF1 to a larger value, while setting the distribution ratio DR2 of the current axial force AF2 to a smaller value. Note that the two distribution ratios DR1 and DR2 used during current limiting are set so that their sum is "1 (100%)." Furthermore, the two distribution ratios DR1 and DR2 used during current limiting are set to appropriate values ​​based on product specifications, etc. Specific examples of the settings for the two distribution ratios DR1 and DR2 are as follows.

[0150] When the code "1A" is acquired, that is, the heating state of the turning motor 41 is a slightly overheated state, the distribution ratio calculator 81E sets the values ​​of the two distribution ratios DR1, DR2 as expressed by the following relational expression (8).

[0151] DR1:DR2=0.8(80%):0.2(20%)…(8)

[0152] When the code "1B" is acquired, that is, the heating state of the turning motor 41 is the moderately overheated state, the distribution ratio calculator 81E sets the values ​​of the two distribution ratios DR1, DR2 as expressed by the following relational expression (9).

[0153] DR1:DR2=0.9(90%):0.1(10%)…(9)

[0154] When the code "1C" is acquired, that is, the heating state of the turning motor 41 is a severely overheated state, the distribution ratio calculator 81E sets the values ​​of the two distribution ratios DR1, DR2 as expressed by the following relational expression (10).

[0155] DR1:DR2=1(100%):0(0%)…(10)

[0156] When the DC power supply voltage V b During a decrease, as the degree of decrease worsens in the order of "mild," "moderate," and "severe," the distribution ratio calculator 81E sets the value of the distribution ratio DR1 of the angular axial force AF1 to a larger value, while setting the value of the distribution ratio DR2 of the current axial force AF2 to a smaller value. Note that the two distribution ratios DR1 and DR2 used during current limiting are set so that the sum of the two distribution ratios is "1 (100%)." Furthermore, the two distribution ratios DR1 and DR2 used during current limiting are set to appropriate values ​​according to product specifications, etc. A specific example of the settings of the two distribution ratios DR1 and DR2 is as follows.

[0157] When the code "2A" is acquired, that is, the state of the DC power supply is a slightly reduced voltage state, the distribution ratio calculator 81E sets the values ​​of the two distribution ratios DR1, DR2 as expressed by the following relational expression (11).

[0158] DR1:DR2=0.8(80%):0.2(20%)…(11)

[0159] When the code "2B" is acquired, that is, the state of the DC power supply is the moderately stepped-down state, the distribution ratio calculator 81E sets the values ​​of the two distribution ratios DR1, DR2 as expressed by the following relational expression (12).

[0160] DR1:DR2=0.9(90%):0.1(10%)…(12)

[0161] When the code "2C" is acquired, that is, the state of the DC power supply is the severely reduced voltage state, the distribution ratio calculator 81E sets the values ​​of the two distribution ratios DR1, DR2 as expressed by the following relational expression (13).

[0162] DR1:DR2=1(100%):0(0%)…(13)

[0163] Furthermore, it is conceivable that multiple situations (here, overheating of the turning motor 41 and a reduction in the DC power supply voltage) may occur simultaneously, requiring the current of the turning motor 41 to be limited. To address these situations, codes may be prioritized based on, for example, the type or severity of the state of the steering device 10. For example, code "1C" indicating a severely overheated turning motor 41 may take precedence over code "2A" indicating a slightly reduced DC power supply voltage.

[0164] Therefore, according to the eighth embodiment, the following effects can be obtained. The turning controller 50b sends a code as a symbol indicating the state of the steering device 10 to the reaction force controller 50a. Therefore, the temperature T of the turning motor 41, for example, which is obtained by the turning controller 50b, is m , DC power supply voltage V b Compared with a case where the information is sent directly to the reaction force controller 50a as information indicating the state of the steering device 10, the communication load between the reaction force controller 50a and the turning controller 50b is reduced.

[0165] According to the current I of the turning motor 41 b Depending on the degree of a specific situation that must be limited, such as the degree of overheating of the turning motor 41 or the degree of voltage drop of the DC power supply, the value of the distribution ratio DR1 of the angular axial force AF1 and the value of the distribution ratio DR2 of the current axial force AF2 are increased or decreased. This makes it possible to adjust the current I bThe degree of the specific situation that must be limited is gradually switched between the angular axial force AF1 and the current axial force AF2. b The extent of the specific situation must be limited, gradually ensuring the steering reaction as information for the driver.

[0166] Other Implementations

[0167] The first to eighth embodiments may be modified as follows. In the first to eighth embodiments, instead of the pinion angle θ p The angular axial force calculator 81A can calculate the steering angle θ based on the steering angle calculated by the steering angle calculator 51. s or the target pinion angle θ calculated by the target pinion angle calculator 62 p * The angular axial force AF1 calculated in this way is also the ideal value of the axial force acting on the turning axis 14 according to the steering condition.

[0168] In the first to seventh embodiments, the reaction force controller 50a and the turning controller 50b in the control device 50 may be separate electronic control units (ECUs) independent of each other. In the first to eighth embodiments, the steering device 10 may be provided with a clutch. In this case, Figure 1 As shown by the two-dot chain line in FIG, the steering shaft 12 and the pinion shaft 13 are connected via a clutch 21. An electromagnetic clutch is employed as the clutch 21, which intermittently supplies power by intermittently energizing an excitation coil. The control device 50 performs intermittent control for switching the engagement and disengagement of the clutch 21. When the clutch 21 is disengaged, the power transmission between the steering wheel 11 and the turning wheel 16 is mechanically disconnected. When the clutch 21 is engaged, the power transmission between the steering wheel 11 and the turning wheel 16 is mechanically connected.

Claims

1. A steering control device (50), comprising: a reaction force controller (50a) for controlling a reaction force motor (31) based on a command value calculated according to a steering condition, the reaction force motor (31) being a source of steering reaction force applied to a steering wheel (11), the steering wheel (11) being separated from a turning shaft (14) in terms of power transmission; and a turning controller (50b), which is independent of the reaction force controller (50a) and controls the turning motor (41) according to the steering condition, wherein the turning motor (41) is the source of the turning force applied to the turning shaft (14), and is characterized in that The reaction force controller (50a) comprises: a first calculator (81B) configured to calculate a first axial force acting on the turning shaft (14) based on a current value of the turning motor (41); a second calculator (81A) configured to calculate a second axial force acting on the turning shaft (14) based on other vehicle state variables different from the current value of the turning motor (41); and a third calculator (81C) configured to calculate a third axial force as a final axial force to be reflected in the command value based on the first axial force and the second axial force, wherein When a specific situation occurs in which the current of the turning motor (41) must be limited, the turning controller (50b) sets a code corresponding to the degree of the specific situation and sends the code to the reaction force controller (50a) via the vehicle network. The reaction force controller (50a) is configured to, when the specific situation occurs, reduce the reflection degree of the first axial force in the third axial force and increase the reflection degree of the second axial force in the third axial force based on the code from the turning controller (50b).

2. The steering control device (50) according to claim 1, characterized in that The third calculator (81C) is configured to calculate the third axial force by adding values ​​obtained by multiplying the first axial force and the second axial force by a distribution ratio, the distribution ratio being set respectively according to vehicle behavior, steering conditions, or road conditions, and The reaction force controller (50a) is configured to, when the specific situation occurs, reduce the distribution ratio of the first axial force to the third axial force and increase the distribution ratio of the second axial force to the third axial force based on the code.

3. The steering control device (50) according to claim 2, characterized in that The reaction force controller (50a) further includes a fourth calculator (81E), The fourth calculator (81E) is configured to, when the specific situation occurs, calculate the distribution ratios of the first axial force and the second axial force used in current limitation based on the code and a predetermined foothold, respectively, wherein the predetermined foothold is a foothold at which the distribution ratio of the first axial force relative to the third axial force is further reduced and the distribution ratio of the second axial force relative to the third axial force is further increased, wherein The third calculator (81C) is configured to calculate the third axial force by using the distribution ratio used at the time of the current limitation calculated by the fourth calculator when the specific situation occurs.

4. The steering control device (50) according to claim 3, characterized in that The severity of the specific condition includes mild, moderate, and severe. The fourth calculator (81E) is configured to set the distribution ratio of the first axial force to the third axial force to 0% and to set the distribution ratio of the second axial force to the third axial force to 100% when the code is the code indicating the severity.

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