JP7243045B2 - steering controller - Google Patents

Description

The present invention relates to a steering control device.

Conventionally, an electric power steering system (EPS) using a motor as a drive source has been widely used as a steering system for vehicles. Compensation controls may be implemented. For example, Patent Literature 1 discloses a device that detects the grip state of a tire (for example, a degree of grip loss indicating the degree of loss of grip of the tire) and varies an assist force according to the degree of grip loss. The degree of grip loss is calculated based on the assist torque calculated based on the steering torque, the inertia of the motor that applies the assist torque, and the first self-aligning torque (SATa) calculated based on the frictional force, It is obtained by calculating the difference between the second self-aligning torque (SATb) obtained from the product of the acting lateral force and the trail.

In recent years, in the steer-by-wire type steering system, which has been developed, the power transmission between the steered wheels and the steering wheel is separated. Therefore, the road surface reaction force received by the steered wheels is not mechanically transmitted to the steering wheel. A force is applied by a steering-side actuator (steering-side motor). For example, in Patent Document 2, focusing on the axial force acting on the steering shaft connected to the steered wheels, the ideal axial force calculated from the target steering angle corresponding to the target steering angle of the steering wheel and the steering side A steering control device is disclosed which determines a steering reaction force in consideration of a road axial force calculated from a drive current of a steering-side motor, which is a drive source of an actuator, and a distributed axial force obtained by distributing the road axial force at a predetermined distribution ratio.

Japanese Patent Application Laid-Open No. 2009-40341 JP 2017-165219 A

By the way, in a steering control device that controls a steer-by-wire type steering device, realization of a better steering feeling is required. Therefore, in the configuration of Patent Document 2, the grip state is detected from the difference between the road surface axial force and the ideal axial force, and the steering reaction force to be applied is compensated based on the detection result. It is conceivable to inform the driver of the effects such as grip loss due to

Here, in the same configuration, the road surface axial force is a component reflecting road surface information, but the ideal axial force is the axial force under ideal conditions calculated based on the target steering angle. Therefore, the deviation of the ideal axial force from the axial force actually acting on the steered shaft increases when, for example, the behavior of the vehicle changes. As a result, if the grip state is determined based on the difference between the road surface axial force and the ideal axial force, there is a possibility that an accurate grip state cannot be determined, and it is conceivable that the steering reaction force cannot be compensated appropriately.

The method for detecting the grip state described in Patent Document 1 cannot be applied to a steer-by-wire steering system because the grip loss detection method uses, for example, an assist torque as a parameter used to detect the degree of grip loss.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to provide a steering control device capable of applying an appropriate steering reaction force according to the grip state.

A steering control device that solves the above problems has a structure in which a steering section and a steered section that steers steered wheels according to steering input to the steering section are mechanically separated or mechanically connectable. A steering device having a structure is a control object, and a control unit is provided for controlling the operation of a steering-side motor that provides a steering reaction force that is a force that resists steering input to the steering unit. An ideal axial force calculation unit that calculates an ideal axial force based on a value related to the rotation angle of the rotation shaft that can be converted to a turning angle of the road surface Axial force calculation unit that calculates the road surface axial force based on the road surface information, a vehicle a vehicle state quantity axial force calculation unit for calculating a vehicle state quantity axial force based on a vehicle state quantity that changes according to a running state; a grip state quantity calculation unit that calculates a grip state quantity by calculating a grip component of the grip component and summing the plurality of grip components at a predetermined distribution ratio, and considering the grip state quantity, the target steering reaction force When the running state quantity indicating the running state of the vehicle indicates that the vehicle is in a low speed state including a stopped state, the grip state quantity calculating section calculates the target reaction force torque to be the ideal When the grip state quantity is calculated with a distribution ratio including the first grip component based on the axial force and the road surface axial force, and the running state quantity indicates that the vehicle is in a medium-high speed state faster than the stopped state, The grip state quantity is calculated with a distribution ratio including at least a second grip component based on the vehicle state quantity axial force.

Since the axial force acting on the steering shaft changes depending on the behavior of the vehicle, the axial force actually acting on the steering shaft can be calculated by using the vehicle state quantity axial force based on the vehicle state quantity. can be estimated more accurately than the ideal axial force. However, when the running state of the vehicle is in a low-speed state including a stopped state, the vehicle state quantity becomes small. grow to In this case, the vehicle state quantity cannot accurately detect the axial force compared to the value related to the rotation angle of the rotating shaft. In this regard, according to the above configuration, when the running state quantity is in a low speed state and the accuracy of the vehicle state quantity axial force cannot be ensured, the distribution ratio including the first grip component based on the ideal axial force and the road surface axial force to calculate the grip state quantity. Then, when the running state quantity is in the middle/high speed state and the accuracy of the vehicle state quantity axial force can be ensured, the grip state quantity is calculated with a distribution ratio including at least the second grip component based on the vehicle state quantity axial force. . Therefore, an appropriate grip state quantity can be calculated, and the steering reaction force can be appropriately compensated in consideration of the grip state quantity.

In the above steering control device, the grip state quantity calculating section calculates the grip state quantity such that the distribution ratio of the second grip component increases as the running state quantity approaches the middle/high speed state from the low speed state. preferably.

According to the above configuration, as the running state quantity approaches from the low speed state to the middle/high speed state, the distribution ratio of the second grip component increases, so that the grip state quantity can be calculated more appropriately.
In the above steering control device, the grip state quantity calculation unit calculates the grip state quantity at a distribution ratio including only the first grip component when the running state quantity indicates the low speed state. is preferred.

According to the above configuration, when the running state quantity indicates a low speed state, only the first grip component is included, that is, the grip state quantity is obtained without using the second grip component based on the vehicle state quantity axial force. Calculate. The first grip component is a value based on the ideal axial force that is highly accurate in the low speed state of the vehicle, and is not based on the vehicle state quantity axial force that is less accurate in the medium to high speed state of the vehicle. Grip state quantity can be calculated.

In the above steering control device, the grip state quantity calculation unit calculates the grip state quantity with a distribution ratio that includes only the second grip component when the running state quantity indicates that the running state quantity is in the medium-high speed state. preferably.

According to the above configuration, only the second grip component is included when the running state quantity indicates the medium-high speed state, that is, the grip is performed without using the first grip component based on the ideal axial force and the road surface axial force. Calculate the state quantity. The second grip component is a value based on the vehicle state quantity axial force that is accurate in the medium to high speed state of the vehicle, and is not based on the ideal axial force that is less accurate in the medium to high speed state of the vehicle. can calculate the grip state quantity.

In the above steering control device, it is preferable that the running state quantity includes at least one of lateral acceleration and vehicle speed.
According to the above configuration, the running state of the vehicle can be determined based on the appropriate running state quantity, and the grip state quantity can be calculated.

According to the present invention, an appropriate steering reaction force can be applied according to the grip state.

1 is a schematic configuration diagram of a steer-by-wire steering system according to a first embodiment; FIG. 1 is a block diagram of a steering control device according to a first embodiment; FIG. FIG. 2 is a block diagram of a target steering angle calculator according to the first embodiment; FIG. FIG. 4 is a block diagram of a grip state quantity calculator according to the first embodiment; FIG. 4 is a schematic diagram showing the relationship between the lateral force acting on the point of force application, the self-aligning torque, and the pneumatic trail. Graphs showing changes in ideal axial force, lateral force (vehicle state dual axial force), self-aligning torque (road surface axial force), and pneumatic trail with respect to changes in slip angle. FIG. 3 is a block diagram of an adjustment gain calculator according to the first embodiment; The block diagram of the grip state quantity calculation part of 2nd Embodiment. The block diagram of the target steering angle calculating part of 3rd Embodiment. The block diagram of the steering control apparatus of 4th Embodiment. FIG. 11 is a block diagram of a target steering corresponding angle calculator according to the fourth embodiment; FIG. 11 is a block diagram of a target steering corresponding angle calculation unit according to a fifth embodiment; FIG. 5 is a schematic configuration diagram of a steer-by-wire steering system according to a modification;

(First embodiment)
A first embodiment of the steering control device will be described below with reference to the drawings.
As shown in FIG. 1, a steer-by-wire steering device 2 to be controlled by a steering control device 1 includes a steering unit 3 steered by a driver and steered wheels 4 according to the steering of the steering unit 3 by the driver. and a steering portion 5 for steering.

The steering unit 3 includes a steering shaft 12 to which a steering wheel 11 is fixed, and a steering-side actuator 13 capable of applying a steering reaction force to the steering shaft 12 . The steering-side actuator 13 includes a steering-side motor 14 that serves as a drive source, and a steering-side reduction gear 15 that decelerates rotation of the steering-side motor 14 and transmits the reduced rotation to the steering shaft 12 .

The steered portion 5 includes a first pinion shaft 21 as a rotation shaft that can be converted into a steered angle of the steered wheels 4, a rack shaft 22 as a steered shaft connected to the first pinion shaft 21, and a rack shaft 22. and a rack housing 23 that reciprocally accommodates the . The first pinion shaft 21 and the rack shaft 22 are arranged with a predetermined crossing angle. A first rack-and-pinion mechanism 24 is constructed by meshing the . The rack shaft 22 is supported by a first rack-and-pinion mechanism 24 so that one axial end thereof can reciprocate. A tie rod 26 is connected to both ends of the rack shaft 22 via a rack end 25 consisting of a ball joint, and the tip of the tie rod 26 is connected to a knuckle (not shown) to which the steered wheels 4 are assembled.

Further, the steering portion 5 is provided with a steering-side actuator 31 that imparts a steering force for steering the steered wheels 4 to the rack shaft 22 via a second pinion shaft 32 . The steering-side actuator 31 includes a steering-side motor 33 that serves as a drive source, and a steering-side reduction gear 34 that decelerates rotation of the steering-side motor 33 and transmits the reduced rotation to the second pinion shaft 32 . The second pinion shaft 32 and the rack shaft 22 are arranged with a predetermined crossing angle. A second rack-and-pinion mechanism 35 is constructed by meshing the . The rack shaft 22 is supported by the second rack-and-pinion mechanism 35 so that the other axial end thereof can reciprocate.

In the steering device 2 configured as described above, the second pinion shaft 32 is rotationally driven by the steering-side actuator 31 according to the steering operation by the driver, and this rotation of the rack shaft 22 is caused by the second rack-and-pinion mechanism 35 . The steered angle of the steered wheels 4 is changed by conversion into axial movement. At this time, the steering-side actuator 13 applies a steering reaction force to the steering wheel 11 against steering by the driver.

Next, the electrical configuration of this embodiment will be described.
The steering control device 1 is connected to a steering-side actuator 13 (steering-side motor 14) and a steering-side actuator 31 (steering-side motor 33), and controls these operations. The steering control device 1 includes a central processing unit (CPU) and a memory (not shown), and various controls are executed by the CPU executing a program stored in the memory at predetermined calculation cycles.

A vehicle speed sensor 41 for detecting a vehicle speed V and a torque sensor 42 for detecting a steering torque Th applied to the steering shaft 12 are connected to the steering control device 1 . The torque sensor 42 is provided on the steering wheel 11 side of the connecting portion of the steering shaft 12 with the steering actuator 13 (steering reduction gear 15). The steering control device 1 also includes a steering-side rotation sensor 43 for detecting the rotation angle .theta.s of the steering-side motor 14 at a relative angle within a range of 360.degree. A steering-side rotation sensor 44 is connected to detect the rotation angle .theta.t of the steering-side motor 33 as a detection value indicating the steering amount of 5 as a relative angle. A yaw rate sensor 45 for detecting a yaw rate γ of the vehicle and a lateral acceleration sensor 46 for detecting a lateral acceleration LA of the vehicle are connected to the steering control device 1 . Note that the steering torque Th and the rotation angles θs and θt have a positive value when steering in one direction (right in this embodiment) and a negative value when steering in the other direction (left in this embodiment). Detect as Then, the steering control device 1 controls the operations of the steering-side motor 14 and the steering-side motor 33 based on these various state quantities.

The configuration of the steering control device 1 will be described in detail below.
As shown in FIG. 2, the steering control device 1 includes a steering-side control unit 51 as a control unit that outputs a steering-side motor control signal Ms, and supplies driving power to the steering-side motor 14 based on the steering-side motor control signal Ms. and a steering-side drive circuit 52 for supplying power. The steering-side control unit 51 detects phase current values Ius, Ivs, and Iws of the steering-side motor 14 flowing through connection lines 53 between the steering-side drive circuit 52 and the motor coils of the respective phases of the steering-side motor 14. A current sensor 54 is connected. In addition, in FIG. 2, for convenience of explanation, the connection lines 53 of each phase and the current sensors 54 of each phase are collectively illustrated as one.

The steering control device 1 also includes a steering-side control unit 55 that outputs a steering-side motor control signal Mt, and a steering-side motor 33 that supplies drive power to the steering-side motor 33 based on the steering-side motor control signal Mt. and a drive circuit 56 . The steering-side control unit 55 stores current values Iut, Ivt, and current values Iut, Ivt, and Iut of each phase of the steering-side motor 33 flowing through a connection line 57 between the steering-side drive circuit 56 and the motor coils of the respective phases of the steering-side motor 33 . A current sensor 58 is connected to detect Iwt. In addition, in FIG. 2, for convenience of explanation, the connection lines 57 of each phase and the current sensors 58 of each phase are shown together as one. A well-known PWM inverter having a plurality of switching elements (for example, FETs, etc.) is adopted for each of the steering-side drive circuit 52 and the turning-side drive circuit 56 of the present embodiment. The steering-side motor control signal Ms and the turning-side motor control signal Mt are gate on/off signals that define the on/off state of each switching element.

The steering control device 1 executes each arithmetic processing shown in each control block below at each predetermined arithmetic cycle to generate a steering-side motor control signal Ms and a steering-side motor control signal Mt. The steering motor control signal Ms and the turning motor control signal Mt are output to the steering driving circuit 52 and the turning driving circuit 56 to turn on and off each switching element, thereby turning the steering motor 14 and the steering motor 14 on and off. Drive power is supplied to each of the side motors 33 . Accordingly, the operations of the steering-side actuator 13 and the steering-side actuator 31 are controlled.

First, the configuration of the steering-side control section 51 will be described.
The steering-side control unit 51 receives the vehicle speed V, steering torque Th, rotation angle θs, lateral acceleration LA, yaw rate γ, phase current values Ius, Ivs, Iws, and q-axis current value Iqt. Then, the steering-side control section 51 generates and outputs a steering-side motor control signal Ms based on these state quantities.

Specifically, the steering control unit 51 includes a steering angle calculation unit 61 that calculates the steering angle θh of the steering wheel 11 based on the rotation angle θs of the steering motor 14, and a target steering angle θh* based on the steering torque Th. and a target steering angle calculator 64 for generating the target steering angle. Further, the steering-side control unit 51 includes a target reaction torque calculation unit 65 that calculates a target reaction torque Ts* based on the steering angle θh and the target steering angle θh*, and a steering-side control unit 65 that calculates a target reaction torque Ts* based on the target reaction torque Ts*. and a steering-side motor control signal generator 66 that generates a motor control signal Ms. Further, the steering control unit 51 includes a grip state quantity calculator 67 that calculates the grip state quantity Gr, and an adjustment gain calculator 68 that changes the first to fourth adjustment gains K1 to K4 according to the grip state quantity Gr. It has

The steering angle calculator 61 obtains the input rotation angle θs by converting it into an absolute angle exceeding 360°, for example, by counting the number of rotations of the steering-side motor 14 from the steering neutral position. Then, the steering angle calculator 61 calculates the steering angle θh by multiplying the absolute angle-converted rotation angle by a conversion coefficient Ks based on the rotation speed ratio of the steering-side reduction gear 15 .

The vehicle speed V, the steering torque Th, the first to fourth adjustment gains K1 to K4, and the q-axis current value Iqt of the steering motor 33 are input to the target steering angle calculator 64 . Then, the target steering angle calculator 64 calculates a target steering angle θh* based on these state quantities, and outputs it to the subtractor 69 and the steering control unit 55, as will be described later.

In addition to the input torque basic component Tb* output from the target steering angle calculation unit 64 described later, the target reaction force torque calculation unit 65 receives an angle deviation obtained by subtracting the steering angle θh from the target steering angle θh* in the subtractor 69. Δθs is entered. Based on the angular deviation Δθs, the target reaction force torque calculation unit 65 provides a basis for the steering reaction force applied by the steering-side motor 14 as a control amount for feedback-controlling the steering angle θh to the target steering angle θh*. A reaction torque is calculated, and an input torque basic component Tb* is added to the basic reaction torque to calculate a target reaction torque Ts*. Specifically, the target reaction torque calculator 65 calculates the sum of the output values of the proportional element, the integral element, and the differential element to which the angular deviation Δθs is input, as the basic reaction torque.

In addition to the target reaction torque Ts*, the rotation angle θs and the phase current values Ius, Ivs, and Iws are input to the steering-side motor control signal generator 66 . The steering-side motor control signal generator 66 of this embodiment calculates a q-axis target current value Iqs* on the q-axis in the d/q coordinate system based on the target reaction torque Ts*. In this embodiment, the d-axis target current value Ids* on the d-axis is set to zero.

The steering-side motor control signal generator 66 generates (calculates) the steering-side motor control signal Ms to be output to the steering-side drive circuit 52 by executing current feedback control in the d/q coordinate system. Specifically, the steering-side motor control signal generation unit 66 maps the phase current values Ius, Ivs, and Iws onto the d/q coordinates based on the rotation angle θs, so that the steering-side motor control signal generator 66 A d-axis current value Ids and a q-axis current value Iqs, which are actual current values of 14, are calculated. Then, the steering-side motor control signal generator 66 adjusts the d A voltage command value is calculated based on each current deviation on the axis and the q-axis, and a steering-side motor control signal Ms having a duty ratio based on the voltage command value is generated. By outputting the steering-side motor control signal Ms thus calculated to the steering-side drive circuit 52, driving power corresponding to the steering-side motor control signal Ms is output to the steering-side motor 14, thereby controlling its operation. be done.

Next, the steering-side control section 55 will be described.
The rotation angle θt, the target steering angle θh*, and the phase current values Iut, Ivt, and Iwt of the steering-side motor 33 are input to the steering-side control unit 55 . Then, the steering-side control section 55 generates and outputs a steering-side motor control signal Mt based on these state quantities.

Specifically, the steered-side control unit 55 calculates a steered corresponding angle θp corresponding to the rotation angle (pinion angle) of the first pinion shaft 21 , which is a rotation axis convertible to the steered angle of the steered wheels 4 . A rudder correspondence angle calculator 71 is provided. Further, the steering-side control unit 55 includes a target steering torque calculation unit 72 that calculates a target steering torque Tt* based on the steering corresponding angle θp and the target steering angle θh*, and a target steering torque calculation unit 72 that calculates a target steering torque Tt* based on the target steering torque Tt*. and a steering-side motor control signal generator 73 for generating a steering-side motor control signal Mt. In the steering device 2 of the present embodiment, the steering angle ratio, which is the ratio between the steering angle θh and the steering corresponding angle θp, is set constant, and the target steering corresponding angle is equal to the target steering angle θh*. .

The steering corresponding angle calculator 71 converts the input rotation angle θt into an absolute angle exceeding 360° by counting the number of revolutions of the steering motor 33 from a neutral position where the vehicle travels straight, for example. to obtain. Then, the steered corresponding angle calculation unit 71 converts the rotation angle converted to the absolute angle into a conversion based on the rotation speed ratio of the steered side reduction gear 34 and the rotation speed ratio of the first and second rack and pinion mechanisms 24 and 35. A turning corresponding angle θp is calculated by multiplying the coefficient Kt. That is, the steered corresponding angle θp corresponds to the steering angle θh of the steering wheel 11 assuming that the first pinion shaft 21 is connected to the steering shaft 12 .

The target steering torque calculator 72 receives an angle deviation Δθp obtained by subtracting the steering corresponding angle θp from the target steering angle θh* (target steering corresponding angle) in a subtractor 74 . Based on the angular deviation Δθp, the target steering torque calculation unit 72 calculates the steering force applied by the steering-side motor 33 as a control amount for feedback-controlling the steering corresponding angle θp to the target steering angle θh*. A target steering torque Tt*, which is a target value, is calculated. Specifically, the target turning torque calculation unit 72 calculates the sum of the output values of the proportional element, the integral element, and the differential element to which the angular deviation Δθp is input, as the target turning torque Tt*.

In addition to the target steering torque Tt*, the rotation angle θt and the phase current values Iut, Ivt, and Iwt are input to the steering-side motor control signal generator 73 . Then, the steering-side motor control signal generator 73 calculates a q-axis target current value Iqt* on the q-axis in the d/q coordinate system based on the target steering torque Tt*. In this embodiment, the d-axis target current value Idt* on the d-axis is set to zero.

The steering-side motor control signal generator 73 generates (calculates) a steering-side motor control signal Mt to be output to the steering-side drive circuit 56 by executing current feedback control in the d/q coordinate system. Specifically, the steering-side motor control signal generation unit 73 maps the phase current values Iut, Ivt, and Iwt onto the d/q coordinates based on the rotation angle θt, thereby generating a steering signal in the d/q coordinate system. A d-axis current value Idt and a q-axis current value Iqt, which are actual current values of the side motor 33, are calculated. Then, the steering-side motor control signal generator 73 causes the d-axis current value Idt to follow the d-axis target current value Idt* and the q-axis current value Iqt to follow the q-axis target current value Iqt*. A voltage command value is calculated based on the current deviation on the d-axis and the q-axis, and a steering-side motor control signal Mt having a duty ratio based on the voltage command value is generated. By outputting the steering-side motor control signal Mt calculated in this manner to the steering-side drive circuit 56, drive power corresponding to the steering-side motor control signal Mt is output to the steering-side motor 33, Its operation is controlled. The q-axis current value Iqt calculated in the process of generating the steering-side motor control signal Mt is output to the target steering angle calculator 64 .

Next, the configuration of the target steering angle calculator 64 will be described.
As shown in FIG. 3 , the target steering angle computing unit 64 includes an input torque basic component computing unit 81 that computes an input torque basic component Tb*, which is the force that rotates the steering wheel 11 , and an input torque basic component computing unit 81 that acts against the rotation of the steering wheel 11 . and a reaction force component calculator 82 for calculating a reaction force component Fir, which is a force. The target steering angle calculator 64 also includes a target angle calculator 83 that calculates the target steering angle θh* based on the steering torque Th, the input torque basic component Tb*, and the reaction force component Fir.

The steering torque Th is input to the input torque basic component calculator 81 . The input torque basic component calculation unit 81 calculates an input torque basic component (reaction force basic component) Tb* having a larger absolute value as the absolute value of the steering torque Th increases, and the multiplier 84 and the target reaction torque calculation unit 81 Output to unit 65 . The multiplier 84 calculates an input torque basic component Tb*' by multiplying the input torque basic component Tb* by a first adjustment gain K1 output from an adjustment gain calculator 68, which will be described later. The input torque base component Tb*' is input to an adder 85 together with the steering torque Th. The adder 85 calculates the drive torque Tc by adding the steering torque Th to the input torque basic component Tb*', and outputs the result to the subtractor 86. In addition to the drive torque Tc, the subtractor 86 receives a reaction force component Fir calculated by a reaction force component calculation section 82, which will be described later. Then, the input torque Tin* is calculated by subtracting the reaction force component Fir from the driving torque Tc in the subtractor 86 .

The input torque Tin*, the vehicle speed V, and the second and third adjustment gains K2 and K3 are input to the target angle calculation processing unit 83 . The target angle calculation processing unit 83 of the present embodiment calculates the target steering angle θh* using the following model (steering model) expression (1) that relates the input torque Tin* and the target steering angle θh*. .

Tin*=K3.C..theta.h*'+(J/K2)..theta.h*'' (1)
This model formula expresses the torque and rotation It defines and expresses the relationship with the angle. This model formula is expressed using a viscosity coefficient C that models the friction and the like of the steering device 2 and an inertia coefficient J that models the inertia of the steering device 2 . Note that the viscosity coefficient C and the inertia coefficient J are variably set according to the vehicle speed V. FIG. Also, the second and third adjustment gains K2 and K3 are output from an adjustment gain calculator 68, which will be described later. The target steering angle θh* thus calculated using the model formula is output to the reaction force component calculation section 82 in addition to the subtractor 69 and steering side control section 55 (see FIG. 2).

Next, the configuration of the reaction force component calculator 82 will be described.
The vehicle speed V, the target steering angle θh*, the phase current values Iut, Ivt, and Iwt, which are the actual current values of the steering-side motor 33, and the fourth adjustment gain K4 are input to the reaction force component calculator 82 . The reaction force component calculator 82 calculates a reaction force component Fir (base reaction force) corresponding to the axial force acting on the rack shaft 22 based on these state quantities, and outputs it to the subtractor 86 .

The reaction force component calculation unit 82 includes a road surface axial force calculation unit 91 that calculates the road surface axial force Fer and an ideal axial force calculation unit 92 that calculates the ideal axial force Fib. The road surface axial force Fer and the ideal axial force Fib are calculated in terms of torque (N·m). In addition, the reaction force component calculation unit 82 calculates the ideal axial force Fib and the road surface axial force Fer by a predetermined ratio so that the axial force applied to the steered wheels 4 from the road surface (road surface information transmitted from the road surface) is reflected. is provided with a distributed axial force calculation unit 93 for calculating the distributed axial force Fd distributed in .

The target steering angle θh* (target steering corresponding angle) and the vehicle speed V are input to the ideal axial force calculator 92 . The ideal axial force calculator 92 converts the ideal axial force Fib, which is an ideal value of the axial force acting on the steered wheels 4 (transmission force transmitted to the steered wheels 4) and does not reflect the road surface information, into the target steering angle θh*. calculated based on Specifically, the ideal axial force calculation unit 92 calculates such that the absolute value of the ideal axial force Fib increases as the absolute value of the target steering angle θh* increases. Further, the ideal axial force calculation unit 92 calculates so that the absolute value of the ideal axial force Fib increases as the vehicle speed V increases. The ideal axial force Fib thus calculated is output to the multiplier 94 and the grip state quantity calculator 67, which will be described later.

A q-axis current value Iqt of the steering-side motor 33 is input to the road surface axial force calculator 91 . A road surface axial force calculation unit 91 converts the road surface axial force Fer, which is an estimated value of the axial force acting on the steered wheels 4 (transmission force transmitted to the steered wheels 4) reflecting the road surface information, into the q-axis current value Iqt. Calculate based on Specifically, the road surface axial force calculation unit 91 assumes that the torque applied to the rack shaft 22 by the steered motor 33 and the torque corresponding to the force applied to the steered wheels 4 from the road surface are balanced. Calculation is performed so that the absolute value of the road axial force Fer increases as the absolute value of the current value Iqt increases. The road surface axial force Fer thus calculated is output to the multiplier 95 and the grip state quantity calculating section 67, which will be described later.

In addition to the vehicle speed V, the road surface axial force Fer and the ideal axial force Fib are input to the distributed axial force calculation unit 93 . A distributed axial force calculation unit 93 includes a distribution gain calculation unit 96 that calculates a distribution gain Gib and a distribution gain Ger, which are respective distribution ratios for distributing the ideal axial force Fib and the road surface axial force Fer based on the vehicle speed V. I have. The distribution gain calculator 96 of this embodiment has a map that defines the relationship between the vehicle speed V and the distribution gains Gib and Ger. do. The distribution gain Gib has a smaller value when the vehicle speed V is high than when it is low, and the distribution gain Ger has a larger value when the vehicle speed V is high than when it is low. In this embodiment, the values are set so that the sum of the distribution gains Gib and Ger is "1". The distribution gain Gib calculated in this way is output to the multiplier 94 and the distribution gain Ger is output to the multiplier 95 .

The distributed axial force calculator 93 multiplies the ideal axial force Fib by the distributed gain Gib in the multiplier 94, multiplies the road axial force Fer by the distributed gain Ger in the multiplier 95, and adds these values in the adder 97. In addition, the distributed axial force Fd is calculated. Then, the reaction force component calculation section 82 calculates a value obtained by multiplying the distributed axial force Fd by a fourth adjustment gain K4, which will be described later, in the multiplier 98 as the reaction force component Fir, and outputs the result to the subtractor 86 described above.

Next, the grip state quantity calculator 67 will be described.
As shown in FIG. 2, the ideal axial force Fib, the road surface axial force Fer, the vehicle speed V, the yaw rate γ, and the lateral acceleration LA are input to the grip state quantity calculator 67 . The grip state quantity calculator 67 calculates the grip state quantity Gr based on these state quantities.

More specifically, as shown in FIG. 4, the grip state quantity calculating section 67 includes a vehicle state quantity axial force calculating section 101 for calculating the vehicle state quantity axial force Fyr. The vehicle state quantity axial force Fyr is calculated in terms of torque (N·m). A yaw rate γ and a lateral acceleration LA as vehicle state quantities are input to the vehicle state quantity axial force calculator 101 . Vehicle state quantity axial force calculator 101 calculates lateral force Fy by inputting yaw rate γ and lateral acceleration LA into the following equation (2).

Lateral force Fy=Kla×Lateral acceleration LA+Kγ×γ' (2)
In addition, "γ'" indicates a differential value of the yaw rate γ, and "Kla" and "Kγ" indicate coefficients preset by tests or the like. Based on the fact that the lateral force Fy thus calculated can be approximately regarded as the axial force acting on the rack shaft 22, the vehicle state quantity axial force calculation unit 101 calculates the lateral force Fy as the vehicle state quantity axis. Output as force Fyr.

Here, the relationship between the slip angle β of the steered wheels and the force acting on the steered wheels will be described with reference to FIGS. 5 and 6. FIG.
FIG. 5 is a top view of the tread of the steerable wheel with a slip angle β. The center line x pointing in the direction of the steerable wheels indicates the original steerable wheel direction, while the direction of travel of the steerable wheels is indicated by line α against this. In the figure, if point A is the contact start point of the steerable wheels and point B is the contact end point, the tread surface is dragged by the road surface by the slip angle β and deviates from the center line x along the line α. bends. In addition, in FIG. 5 , hatching indicates a region in which the tread surface is shifted and bent. Of this bent area, the area on the A point side is the adhesive area, and the area on the B point side is the sliding area. Lateral force Fy acts on the force application point of the contact surface of the steered wheel when turning at such a slip angle β, and the moment about the vertical axis becomes self-aligning torque SAT. The pneumatic trail is the distance between the ground contact center of the steered wheels and the force application point, and the sum of the pneumatic trail and the caster trail is the trail.

FIG. 6 shows changes in ideal axial force Fib, lateral force Fy (vehicle state quantity axial force Fyr), self-aligning torque SAT (road surface axial force Fer), and pneumatic trail with respect to changes in slip angle β. . As shown in the figure, in the region where the slip angle β is small, the ideal axial force Fib, the lateral force Fy, and the self-aligning torque SAT increase approximately linearly as the slip angle β increases. and the difference between each of these values is small. On the other hand, in a region where the slip angle β is large to some extent, the ideal axial force Fib continues to increase substantially linearly as the slip angle β increases, but the lateral force Fy continues to increase and then shows a substantially constant or slightly decreasing tendency. Also, the self-aligning torque SAT continues to increase for a while as the slip angle β increases, but exhibits a tendency to greatly decrease as the pneumatic trail decreases. In this way, the region where each value changes approximately linearly and the difference between them is small is defined as the normal region, and the region where the lateral force Fy and the self-aligning torque SAT change non-linearly and the difference between them becomes large is defined as the limit region. . Note that the division between the normal area and the limit area shown in FIG. 6 is for convenience.

Here, if the axial force during turning is regarded as the self-aligning torque SAT, the relationship between the self-aligning torque SAT and the lateral force Fy is as shown in FIG. It can be expressed by the following equation (3) using parameters corresponding to the pneumatic trail up to the force application point.

Self-aligning torque SAT = lateral force Fy x pneumatic trail (3)
Considering that the self-aligning torque SAT is "axial force ≈ reaction force from the road surface", the road axial force Fer based on the driving current (that is, the q-axis current value Iqt) of the steering-side motor 33 is the self-aligning torque. It can be said that it approximates SAT.

Further, the lateral force Fy is the force generated in the steered wheels 4, and can be approximated by the lateral acceleration LA by replacing with "lateral force Fy ≈force generated in the lateral direction of the vehicle". be able to. Since the lateral acceleration LA alone does not provide sufficient responsiveness to the actual axial force when the vehicle starts to move, the differential of the yaw rate γ is added to improve the responsiveness, and the above equation (2) is obtained.

Further, the grip state quantity Gr, which is a degree of grip indicating how much the steered wheels 4 are gripping, can be expressed by the following equation (4) from the above equation (3).
Grip state quantity Gr=self-aligning torque SAT/lateral force Fy (4)
Considering that the road surface axial force Fer can approximately express the self-aligning torque SAT, and the vehicle state quantity axial force Fyr can approximately express the lateral force, the grip state quantity Gr can be expressed by the following equation (5). can be expressed as

Grip state quantity Gr=(Ker×road surface axial force)/(Ky×vehicle state quantity axial force) (5)
"Ker" and "Ky" indicate coefficients preset by tests or the like.
Here, since the vehicle state changes according to the running state, by using the vehicle state quantity axial force Fyr based on the yaw rate γ and the lateral acceleration LA, the rack shaft 22 can actually move when the behavior of the vehicle changes greatly. The acting axial force can be estimated accurately compared with the ideal axial force Fib. However, the yaw rate γ and the lateral acceleration LA are small when the vehicle is in a low speed state including a stopped state. grow to In this case, the yaw rate γ and the lateral acceleration LA cannot accurately detect the axial force compared to the target steering angle θh*.

Based on this point, as shown in FIG. 4, the grip state quantity calculation unit 67 of the present embodiment includes a first grip component calculation unit 102 that calculates the first grip component Gr1 based on the ideal axial force Fib and the road surface axial force Fer. and a second grip component calculation unit 103 for calculating a second grip component Gr2 based on the vehicle state quantity axial force Fyr and the road surface axial force Fer. Then, when the vehicle speed V and the lateral acceleration LA, which are the running state quantities indicating the running state of the vehicle, indicate that the vehicle is in a low speed state, the grip state quantity calculation unit 67 uses a distribution ratio that includes the first grip component Gr1. A grip state quantity Gr is calculated. On the other hand, when the vehicle speed V and the lateral acceleration LA indicate that the vehicle is in the middle/high speed state, the grip state quantity calculating section 67 calculates the grip state quantity with a distribution ratio including the second grip component Gr2.

Specifically, the road surface axial force Fer and the ideal axial force Fib are input to the first grip component calculation unit 102 . The first grip component calculator 102 calculates the first grip component Gr1 by dividing the road surface axial force Fer by the ideal axial force Fib, and outputs the result to the multiplier 104 . When the absolute value of the ideal axial force Fib is equal to or less than the zero threshold value F0, the first grip component calculation unit 102 of this embodiment does not divide the road surface axial force Fer by the ideal axial force Fib, and calculates the first grip component Gr1 as Output as "0". In other words, the first grip component computing section 102 has a zero dividing prevention function that prevents the first grip component Gr1 from diverging by dividing the road surface axial force Fer by zero. Note that the zero threshold F0 is set to a very small value close to zero. The road surface axial force Fer and the vehicle state quantity axial force Fyr are input to the second grip component calculation unit 103 . The second grip component calculator 103 calculates the second grip component Gr2 by dividing the road surface axial force Fer by the vehicle state quantity axial force Fyr, and outputs the second grip component Gr2 to the multiplier 105 . The second grip component calculation unit 103 of the present embodiment has a function of preventing division by zero. Output Gr2 as "0".

The grip state quantity calculation unit 67 includes a distribution ratio setting unit 106 that sets the distribution ratio Ggr between the first grip component Gr1 and the second grip component Gr2. Vehicle speed V and lateral acceleration LA are input to distribution ratio setting unit 106 . The distribution ratio setting unit 106 has a map as shown in FIG. 4, and sets the distribution ratio Ggr by referring to the map. In this map, the distribution ratio Ggr is set such that the ratio of the second grip component Gr2 increases as the vehicle speed V and the lateral acceleration LA approach from values indicating a low speed state to values indicating a middle to high speed state.

Specifically, when the lateral acceleration LA is equal to or less than the lateral acceleration threshold LAth, the distribution ratio Ggr is "0", and when the lateral acceleration LA exceeds the lateral acceleration threshold LAth, the lateral acceleration LA is It is set so that the allocation ratio Ggr increases with the increase, and then the allocation ratio Ggr becomes constant. Further, the allocation ratio Ggr becomes "0" when the vehicle speed V is equal to or lower than the vehicle speed threshold Vth, and when the vehicle speed V exceeds the vehicle speed threshold Vth, the allocation ratio Ggr decreases as the vehicle speed V increases. set to be large. Note that the maximum value of the distribution ratio Ggr is set to "1". Further, the lateral acceleration threshold value LAth and the vehicle speed threshold value Vth are set in advance through experiments or the like, and are values that have large detection values with respect to noise and can ensure the accuracy of the sensors. When the lateral acceleration LA is equal to or less than the lateral acceleration threshold LAth, the value of the lateral acceleration LA indicates that the vehicle is running at low speed. indicates that the value of the lateral acceleration LA indicates that the running state of the vehicle is middle to high speed. Similarly, when the vehicle speed V is equal to or less than the vehicle speed threshold Vth, the value of the vehicle speed V indicates that the vehicle is running at a low speed. The value of V indicates that the running state of the vehicle is middle to high speed.

The distribution ratio Ggr set in this manner is output to the subtractor 107 and multiplier 105 . In addition to the distribution ratio Ggr, the constant “1” is always input to the subtractor 107 , and a value obtained by subtracting the distribution ratio Ggr from the constant “1” is output to the multiplier 104 . That is, the sum of the allocation ratio of the first grip component Gr1 and the allocation ratio of the second grip component Gr2 is set to be "1".

The grip state quantity calculation unit 67 multiplies the first grip component Gr1 by the output value (1-distribution ratio Ggr) from the subtractor 107 in the multiplier 104, and outputs it to the grip calculation processing unit 108 as the first grip distribution quantity Agr1. Output. Further, the grip state quantity calculation unit 67 outputs a value obtained by multiplying the second grip component Gr2 by the distribution ratio Ggr in the multiplier 105 to the grip calculation processing unit 108 as the second grip distribution quantity Agr2. Then, the grip calculation processing unit 108 outputs a value obtained by adding the first grip allocation amount Agr1 and the second grip allocation amount Agr2 as the grip state amount Gr.

Next, the configuration of the adjustment gain calculator 68 will be described.
As shown in FIG. 2 , the grip state quantity Gr calculated as described above is input to the adjustment gain calculator 68 . As shown in FIG. 7, the adjustment gain calculator 68 includes first to fourth adjustment gain calculators 111 to 114, and the grip state quantity Gr is entered for each.

The first adjustment gain calculator 111 has a map that defines the relationship between the grip state quantity Gr and the first adjustment gain K1. The second adjustment gain calculator 112 has a map that defines the relationship between the grip state quantity Gr and the second adjustment gain K2. The third adjustment gain calculator 113 has a map that defines the relationship between the grip state quantity Gr and the third adjustment gain K3. The fourth adjustment gain calculator 114 has a map that defines the relationship between the grip state quantity Gr and the fourth adjustment gain K4.

In the example shown in FIG. 7, in each map, the first to fourth adjustment gains K1 to K4 are large when the grip state quantity Gr is small, and the first to fourth adjustment gains K1 to K4 are large when the grip state quantity Gr is large. Although K4 is set to be smaller, it is not limited to this relationship. For example, when the grip state quantity Gr is small, the first to fourth adjustment gains K1 to K4 are small, and when the grip state quantity Gr is large, the first to fourth adjustment gains K1 to K4 are set to be large. good too. Also, the tendencies shown by the respective maps may be different from each other. You may set so that K3 may become large respectively.

As shown in FIG. 3, the first adjustment gain K1 thus calculated is output to the multiplier 84 and multiplied by the input torque base component Tb*. As a result, the input torque basic component Tb*' changes according to the first adjustment gain K1. The second adjustment gain K2 is output to the target angle calculation processing section 83 and multiplied by the reciprocal of the inertia coefficient J. As a result, the inertia term changes according to the second adjustment gain K2. The third adjustment gain K3 is output to the target angle calculation processing section 83 and multiplied by the viscosity coefficient C. As a result, the viscosity term changes according to the third adjustment gain K3. The fourth adjustment gain K4 is output to the multiplier 98 and multiplied by the distributed axial force Fd. As a result, the reaction force component Fir changes according to the fourth adjustment gain K4. By changing the first to fourth adjustment gains K1 to K4, the target steering angle θh* changes, and thus the target reaction torque Ts* changes.

Next, changes in the steering feeling accompanying changes in the first to fourth adjustment gains K1 to K4 will be described.
For example, in a situation where the vehicle runs on a low μ road surface and the slip angle β tends to increase, each value of the first to fourth adjustment gains K1 to K4 is ultimately Assume that the target reaction torque Ts* is set to be small. In this case, the steering reaction force applied from the steering-side motor 14 to the steering wheel 11 can be made smaller than usual from the stage before the slip angle β becomes large and enters the limit region. It becomes easier for the driver to recognize the road surface information that the road is a low μ road.

On the other hand, under the same circumstances, the respective values of the first to fourth adjustment gains K1 to K4 are set so as to ultimately increase the target reaction torque Ts* compared to the case where the grip state quantity Gr is not considered. Assume the case. In this case, for example, even when the slip angle β is large, the steering reaction force applied from the steering-side motor 14 to the steering wheel 11 can be increased, and the driver can continue steering without discomfort.

The action and effect of this embodiment will be described.
(1) The grip state quantity calculator 67 indicates that the lateral acceleration LA and the vehicle speed V are in a low speed state, and if the accuracy of the vehicle state quantity axial force Fyr cannot be ensured, the ideal axial force Fib and the road surface axial force Fer The grip state quantity Gr is calculated with a distribution ratio including the first grip component Gr1 based on Then, when the lateral acceleration LA and the vehicle speed V indicate a medium-to-high speed state and the accuracy of the vehicle state quantity axial force Fyr can be ensured, the second grip component based on the vehicle state quantity axial force Fyr and the road surface axial force Fer A grip state quantity Gr is calculated with a distribution ratio including Gr2. Therefore, an appropriate grip state quantity Gr can be calculated, and the steering reaction force can be appropriately compensated in consideration of the grip state quantity Gr.

(2) The grip state quantity calculation unit 67 calculates the grip state quantity so that the distribution ratio of the second grip component Gr2 increases as the lateral acceleration LA and the vehicle speed V approach from a state indicating a low speed state to a state indicating a middle/high speed state. Since Gr is calculated, the grip state quantity Gr can be calculated more appropriately.

(3) Since the distribution ratio setting unit 106 sets the distribution ratio based on the lateral acceleration LA and the vehicle speed V, it is possible to determine the running state of the vehicle based on an appropriate running state quantity and to calculate the grip state quantity Gr.

(Second embodiment)
Next, a second embodiment of the steering control device will be described with reference to the drawings. For convenience of explanation, the same components as those of the first embodiment are denoted by the same reference numerals, and the explanation thereof is omitted.

As shown in FIG. 8, the allocation ratio setting unit 106 of the present embodiment refers to the map shown in FIG. calculates the grip state quantity Gr with the distribution ratio Ggr including only the first grip component Gr1. Further, when both the vehicle speed V and the lateral acceleration LA indicate that the vehicle is in the medium-to-high speed state, the distribution ratio setting unit 106 sets the grip state amount Gr to the distribution ratio Ggr containing only the second grip component Gr2. Calculate. Specifically, the map shown in FIG. The distribution ratio Ggr is set to "1" when the lateral acceleration threshold value LAth is exceeded and the vehicle speed V is greater than the vehicle speed threshold value Vth.

The grip state quantity Gr calculated in this way is input to the adjustment gain calculation section 68 in the same manner as in the first embodiment, and by changing each of the first to fourth adjustment gains K1 to K4, the grip state quantity Gr is changed. The target reaction torque Ts* is changed accordingly.

Next, the action and effect of this embodiment will be described. The present embodiment has the following effects in addition to the actions and effects (1) and (3) of the first embodiment.
(4) When at least one of the lateral acceleration LA and the vehicle speed V indicates that the vehicle is in a low speed state, the grip state quantity calculation unit 67 includes only the first grip component Gr1 based on the ideal axial force Fib. That is, the grip state quantity Gr is calculated without using the second grip component Gr2 based on the vehicle state quantity axial force Fyr. As described above, the first grip component Gr1 is a value based on the ideal axial force Fib, which is highly accurate when the vehicle is in a low speed state, and is not based on the vehicle state quantity axial force Fyr, which is less accurate when the vehicle is in a medium to high speed state. The grip state quantity calculator 67 of the present embodiment can more appropriately calculate the grip state quantity.

(5) When both the lateral acceleration LA and the vehicle speed V indicate that the vehicle is in the medium-to-high speed state, the grip state quantity calculation unit 67 includes only the second grip component Gr2 based on the vehicle state quantity axial force Fyr. That is, the grip state quantity Gr is calculated without using the first grip component Gr1 based on the ideal axial force Fib. As described above, the second grip component Gr2 is a value based on the vehicle state quantity axial force Fyr which is highly accurate in the medium to high speed state of the vehicle, and is not based on the ideal axial force Fib whose accuracy decreases in the medium to high speed state of the vehicle. , the grip state quantity calculator 67 of the present embodiment can more appropriately calculate the grip state quantity Gr.

(Third embodiment)
Next, a third embodiment of the steering control device will be described with reference to the drawings. For convenience of explanation, the same components as those of the first embodiment are denoted by the same reference numerals, and the explanation thereof is omitted.

As shown in FIG. 9, the input torque basic component calculation section 81 of the present embodiment is a torque command value Th* which is a target value of the steering torque Th to be input by the driver with respect to the driving torque Tc. It has a value calculation section 121 and a torque feedback control section (hereinafter referred to as a torque F/B control section) 122 that performs torque feedback calculation.

Specifically, the drive torque Tc obtained by adding the input torque basic component Tb* to the steering torque Th in the adder 123 is input to the torque command value calculation unit 121 . The torque command value calculation unit 121 calculates the torque command value Th*, which has a larger absolute value as the absolute value of the drive torque Tc increases.

A torque deviation ΔT obtained by subtracting the torque command value Th* from the steering torque Th in a subtractor 124 is input to the torque F/B control unit 122 . Based on the torque deviation ΔT, the torque F/B control unit 122 calculates an input torque basic component Tb* as a control amount for feedback-controlling the steering torque Th to the torque command value Th*. Specifically, the torque F/B control unit 122 calculates the sum of the output values of the proportional element, the integral element, and the differential element to which the torque deviation ΔT is input, as the input torque basic component Tb*.

The input torque basic component Tb* calculated in this manner is output to the target reaction force torque calculation unit 65 as in the first embodiment, and is also output to the multiplier 84 and multiplied by the first adjustment gain K1. Thus, the input torque basic component Tb*' is calculated. Accordingly, the target steering angle θh* is changed according to the grip state, and the target reaction torque Ts* is changed.

As described above, the present embodiment has the same actions and effects as the actions and effects (1) to (3) of the first embodiment.
(Fourth embodiment)
Next, a fourth embodiment of the steering control device will be described with reference to the drawings. For convenience of explanation, the same components as those of the first embodiment are denoted by the same reference numerals, and the explanation thereof is omitted.

As shown in FIG. 10, the steering-side control unit 51 of the present embodiment calculates a target steering response angle θp*, which is a target value of the steering response angle θp that can be converted into the steering angle of the steerable wheels 4. The steering corresponding angle calculator 131 is provided, and the target steering angle calculator 64 is not provided. As shown in FIG. 11, the target steering corresponding angle calculator 131 calculates the target steering angle by the same calculation processing as the target steering angle calculator 64 of the first embodiment calculates the target steering angle θh*. Calculate the rudder corresponding angle θp*. For convenience of explanation, the blocks constituting the target steering angle calculating section 131 are assigned the same reference numerals as the blocks constituting the target steering angle calculating section 64 (see FIG. 3).

As shown in FIG. 10 , the target steering response angle θp* calculated by the target steering response angle calculation section 131 is output to the steering control section 55 . Further, the ideal axial force Fib and the road surface axial force Fer are output to the grip state quantity calculator 67 in the same manner as in the first embodiment. Then, the input torque Tin* input to the target angle calculation processing section 83 is inputted from the target steering corresponding angle calculation section 131 to the target reaction force torque calculation section 65 .

The target reaction force torque calculation unit 65 of the present embodiment calculates a target reaction force torque Ts*, which is a target value of the steering reaction force applied by the steering-side motor 14, based on the input torque Tin*. Specifically, the target reaction torque calculation unit 65 calculates the target reaction torque Ts* having a larger absolute value as the input torque Tin* increases. The input torque Tin* has its base input torque basic component Tb* and reaction force component Fir changed by the first and fourth adjustment gains K1 and K4, respectively. As a result, the target reaction torque Ts* based on the input torque Tin* is changed according to the grip state.

As described above, the present embodiment has the same actions and effects as the actions and effects (1) to (3) of the first embodiment.
(Fifth embodiment)
Next, a fifth embodiment of the steering control device will be described with reference to the drawings. For convenience of explanation, the same components as those of the fourth embodiment are denoted by the same reference numerals, and the explanation thereof is omitted.

As shown in FIG. 12, the target steering corresponding angle calculator 131 of the present embodiment outputs the reaction force component Fir to the target reaction force torque calculator 65 and does not output the input torque Tin*. Then, the target reaction torque calculation unit 65 (see FIG. 10) calculates the target reaction torque Ts* having a larger absolute value as the absolute value of the reaction force component Fir increases and as the vehicle speed V increases. Then, the reaction force component Fir is changed by the fourth adjustment gain K4 as described above. As a result, the target reaction force torque Ts* based on the reaction force component Fir is changed according to the grip state.

As described above, the present embodiment has the same actions and effects as the actions and effects (1) to (3) of the first embodiment.
This embodiment can be implemented with the following modifications. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

- In the above-described fourth and fifth embodiments, the target steering corresponding angle θp* is calculated based on the input torque Tin*. good too.

In the above-described second embodiment, when the vehicle speed V and the lateral acceleration LA indicate that the vehicle is in a medium-to-high speed state, the grip state quantity Gr is calculated based only on the second grip component Gr2, and the vehicle speed V and the lateral acceleration LA are calculated. When the acceleration LA indicates that the vehicle is in a low speed state, the grip state quantity Gr may be calculated based on the first and second grip components Gr1 and Gr2. Further, when the vehicle speed V and the lateral acceleration LA indicate that the vehicle is in a low speed state, the grip state quantity Gr is calculated based only on the first grip component Gr1, and the vehicle speed V and the lateral acceleration LA are in a medium high speed state of the vehicle. When indicating the state, the grip state quantity Gr may be calculated based on the first and second grip components Gr1 and Gr2.

- In each of the above-described embodiments, the implementation mode of the zero dividing prevention function can be changed as appropriate. For example, when the absolute value of the vehicle state quantity axial force Fyr is equal to or less than the zero threshold F0, the vehicle state quantity axial force Fyr can be set to a preset lower limit value. Note that the first grip component calculation unit 102 and the second grip component calculation unit 103 do not have to have the division-to-zero prevention function.

In each of the above embodiments, the distribution ratio setting unit 106 sets the distribution ratio Ggr using the lateral acceleration LA and the vehicle speed V as the running state quantities. The allocation ratio Ggr may be set using only one of them. Also, the distribution ratio Ggr may be set using other parameters such as the yaw rate γ.

In each of the above embodiments, the first grip component Gr1 is obtained by dividing the road surface axial force Fer by the ideal axial force Fib. The degree (a value indicating how much the grip of the steered wheels 4 has been lost) may be used as the first grip component Gr1. Similarly, the grip loss degree obtained by subtracting the vehicle state axial force Fyr from the road surface axial force Fer may be used as the second grip component Gr2.

In each of the above embodiments, the first grip component Gr1 based on the road surface axial force Fer and the ideal axial force Fib and the second grip component Gr2 based on the road surface axial force Fer and the vehicle state quantity axial force Fyr are added at a predetermined distribution ratio. The grip state quantity Gr was calculated by However, not limited to this, for example, a third grip component based on the ideal axial force Fib and the vehicle state quantity axial force Fyr is calculated, and the grip state quantity Gr is calculated by adding these grip components at a predetermined distribution ratio. may

・In each of the above embodiments, the road surface axial force Fer was calculated based on the q-axis current value Iqt. It may be used as the axial force Fer.

・In each of the above embodiments, the ideal axial force Fib is calculated based on the target steering angle θh* (target steering corresponding angle) and the vehicle speed V. ) alone, or may be calculated based on the steering corresponding angle θp. Furthermore, other methods such as adding other parameters such as the steering torque Th and the vehicle speed V may be used.

- In each of the above embodiments, the first to fourth adjustment gains K1 to K4 are used as the gains corresponding to the grip state quantity Gr. , a gain that is multiplied by another state quantity may be added.

In each of the above embodiments, the ideal axial force Fib and the road surface axial force Fer are distributed at a predetermined ratio to calculate the distributed axial force Fd. may be distributed at a predetermined ratio to calculate the distributed axial force Fd, and the manner of calculation of the distributed axial force Fd can be changed as appropriate.

In the above embodiment, the vehicle state dual axial force Fyr is calculated based on the yaw rate γ and the lateral acceleration LA. A force Fyr may be calculated.

- In each of the above embodiments, the distributed axial force calculator 93 may calculate the distributed gains Gib and Ger in consideration of parameters other than the vehicle speed V. For example, in a vehicle in which a drive mode indicating the setting state of a control pattern of an in-vehicle engine or the like can be selected from among a plurality of drive modes, the drive mode may be used as a parameter for setting the distribution gains Gib and Ger. In this case, it is possible to adopt a configuration in which the distributed axial force calculation unit 93 is provided with a plurality of maps showing different tendencies with respect to the vehicle speed V for each drive mode, and the distributed gains Gib and Ger are calculated by referring to the maps.

In each of the above embodiments, the reaction force component calculator 82 calculates the base reaction force corresponding to the axial force acting on the rack shaft 22 as the reaction force component Fir. may be calculated as the reaction force component. As such a reaction force, for example, when the absolute value of the steering angle θh of the steering wheel 11 approaches the steering angle threshold value, an end reaction force, which is a reaction force against further cutting steering, can be employed. Note that the steering angle threshold value is, for example, a virtual rack end set on the neutral position side of the mechanical rack end position where the axial movement of the rack shaft 22 is restricted when the rack end 25 comes into contact with the rack housing 23 . It is possible to use the steering corresponding angle θp at a position near the virtual rack end located on the neutral position side by a predetermined angle with respect to the position. Further, the steering angle θh at the rotation end position of the steering wheel 11 can be used as the steering angle threshold.

In each of the above-described embodiments, the target steering angle calculator 64 sets the target steering angle θh* based on the steering torque Th and the vehicle speed V. However, the present invention is not limited to this. For example, vehicle speed V may not be used.

- Although the steering angle ratio between the steering angle θh and the corresponding steering angle θp is constant in each of the above embodiments, the ratio is not limited to this and may be variable according to the vehicle speed or the like. In this case, the target steering angle θh* and the target steering corresponding angle are different values.

In each of the above-described embodiments, the target steering angle calculation unit 64 uses a model formula modeled by adding a so-called spring term using the spring coefficient K determined by the specifications of the suspension, wheel alignment, etc., to achieve the target steering angle. An angle θh* may be calculated.

・In the first to third embodiments, the target reaction torque calculation unit 65 calculates the target reaction torque Ts* by adding the input torque basic component Tb* to the basic reaction torque. For example, the basic reaction torque may be directly calculated as the target reaction torque Ts* without adding the input torque basic component Tb*.

- In each of the above embodiments, instead of the first rack and pinion mechanism 24, the rack shaft 22 may be supported by, for example, a bush.
In each of the above-described embodiments, as the steering-side actuator 31, for example, the steering-side motor 33 is arranged coaxially with the rack shaft 22, or the steering-side motor 33 is arranged parallel to the rack shaft 22. may be used.

In each of the above embodiments, the steering device 2 to be controlled by the steering control device 1 is a linkless steer-by-wire steering device in which the steering section 3 and the steering section 5 are mechanically separated. Alternatively, a steer-by-wire steering system that can mechanically connect and disconnect the steering portion 3 and the steering portion 5 by a clutch may be used.

For example, in the example shown in FIG. 13 , a clutch 301 is provided between the steering section 3 and the steering section 5 . The clutch 301 is connected to the steering shaft 12 via an input-side intermediate shaft 302 fixed to its input-side element, and connected to the first pinion shaft 21 via an output-side intermediate shaft 303 fixed to its output-side element. connected to When the clutch 301 is released by the control signal from the steering control device 1, the steering device 2 enters the steer-by-wire mode, and when the clutch 301 enters the engaged state, the steering device 2 enters the electric power steering mode. .

DESCRIPTION OF SYMBOLS 1... Steering control apparatus 2... Steering apparatus 3... Steering part 4... Steering wheel 5... Steering part 11... Steering wheel 12... Steering shaft 13... Steering side actuator 14... Steering side motor 51 Steering-side control section (control section) 64 Target steering angle calculation section 65 Target reaction force torque calculation section 67 Grip state quantity calculation section 68 Adjustment gain calculation section 81 Input torque basic component calculation section , 82... reaction force component calculation unit 91... road surface axial force calculation unit 92... ideal axial force calculation unit 93... distributed axial force calculation unit 101... vehicle state quantity axial force calculation unit 102... first grip component calculation Section 103 Second grip component calculation section 106 Allocation ratio setting section 111 First adjustment gain calculation section 112 Second adjustment gain calculation section 113 Third adjustment gain calculation section 114 Fourth adjustment Gain calculation section 121 Torque command value calculation section 122 Torque F/B control section 131 Target steering corresponding angle calculation section Ag1 First grip distribution amount Ag2 Second grip distribution amount Fd Distribution Axial force Fer... road surface axial force Fib... ideal axial force Fir... reaction force component Fyr... vehicle state quantity axial force Gr... grip state quantity Gr1... first grip component Gr2... second grip component K1 1st adjustment gain K2 2nd adjustment gain K3 3rd adjustment gain K4 4th adjustment gain LA Lateral acceleration Tb* Input torque basic component Tc Driving torque Th Steering torque Th*: torque command value, Tin*: input torque, Ts*: target reaction torque, Tt*: target steering torque, V: vehicle speed, γ: yaw rate, θh: steering angle, θp: steering corresponding angle, θh *: target steering angle, θp*: target steering corresponding angle.

Claims (4)

A steering device having a structure in which a steering unit and a steering unit that steers steered wheels in accordance with steering input to the steering unit are mechanically separated or mechanically connectable and disconnectable, is controlled,
a control unit for controlling the operation of a steering-side motor that provides a steering reaction force that is a force that resists steering input to the steering unit;
The control unit
an ideal axial force calculation unit that calculates an ideal axial force based on a value related to a rotation angle of a rotating shaft that can be converted into a turning angle of the steered wheels;
a road surface axial force calculation unit that calculates a road surface axial force based on road surface information;
a vehicle state quantity axial force calculation unit that calculates a vehicle state quantity axial force based on a vehicle state quantity that changes according to the running state of the vehicle;
A grip state quantity is calculated by calculating a plurality of grip components based on the ideal axial force, the road surface axial force, and the vehicle state quantity axial force, and adding the plurality of grip components at a predetermined distribution ratio. and a computing unit,
A target reaction force torque, which is a target value of the steering reaction force, is calculated in consideration of the grip state quantity,
The vehicle state quantity is a value including lateral acceleration detected by a sensor provided in the vehicle, and when the running state quantity indicating the running state of the vehicle indicates a low speed state including a stopped state, It has a characteristic that the value is smaller than when the running state quantity indicates that it is a medium-high speed state that is faster than the low speed state,
By indicating that the running state quantity is in the low-speed state, the grip state quantity calculation unit increases the value of the vehicle state quantity compared to the case where the running state quantity indicates that the medium-to-high speed state. when the accuracy of the vehicle state quantity decreases due to the decrease in the grip state quantity , the grip state quantity is calculated with a distribution ratio including the first grip component based on the ideal axial force and the road surface axial force, By indicating that the running state quantity is the medium-high speed state, the value of the vehicle state quantity becomes larger than when the running state quantity indicates that the running state quantity is the low speed state. When the accuracy of the vehicle state quantity is improved , the grip state quantity is calculated at a distribution ratio including at least a second grip component based on the vehicle state quantity axial force,
The grip state quantity calculation unit is a steering control device that calculates the grip state quantity so that the distribution ratio of the second grip component becomes larger when the running state quantity is in the middle/high speed state than in the case of the low speed state. . The steering control device according to claim 1, wherein
The grip state quantity calculation unit calculates the grip state quantity at a distribution ratio including only the first grip component when the running state quantity indicates the low speed state. The steering control device according to claim 1 or 2 ,
The grip state quantity calculation unit calculates the grip state quantity at a distribution ratio including only the second grip component when the running state quantity indicates that the running state quantity is the middle/high speed state. In the steering control device according to any one of claims 1 to 3 ,
The steering control device, wherein the running state quantity includes at least one of lateral acceleration and vehicle speed.

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