Steering system

Abstract

To provide a steer-by-wire type steering system having high practicality.SOLUTION: A controller has: (a) a turning control unit that turns a wheel, based on a steering gear ratio γ; (b) a converted operation amount determination unit 104 that determines a converted operation amount θ'O by converting an actual wheel turning amount θS into an operation amount θO of an operating member, based on an inverse number of the steering gear ratio; and (c) a reaction force control unit that controls an operation reaction force, based on the converted operation amount. In the controller, the converted operation amount determination unit is configured such that: when the steering gear ratio γ suddenly changes, a difference Δθ'O in the converted operation amount arising at the time of the sudden change is converted into a difference Δθ'S in a wheel turning amount, thereby grasping it as a converted turning amount offset value θ'SO; and after the time, while the converted turning amount offset value is gradually reduced, this offset value is re-converted into the difference in a converted operation amount, based on the inverse number of the steering gear ratio, thereby determining a converted operation amount correction value θ'O-C and correcting the converted operation amount with the converted operation amount correction value.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a steer-by-wire type steering system mounted on a vehicle. [Background technology]

[0002] Recently, development has been underway of a system that realizes steering of the wheels in response to the operation of an operating member such as a steering wheel by a steering device having a drive source, without relying on the operating force applied by the driver to the operating member, i.e., a so-called steer-by-wire type steering system (hereinafter, sometimes referred to as a "steer-by-wire system"). In a steer-by-wire system, for example, steering of the wheels is realized such that the ratio of the steering amount of the wheels to the operation amount of the operating member is a set steering gear ratio. On the other hand, in a steer-by-wire system, as described in the following patent document, a reaction force imparting device is provided to impart an operation reaction force, which is a reaction force against the operation of the operating member by the driver (hereinafter, sometimes referred to as a "steering operation"), to the operating member, and the operation reaction force is controlled. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-131072 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to make the operation reaction force of the steer-by-wire system appropriate, for example, it has been considered to convert the actual steering amount of the wheels by multiplying the inverse of the steering gear ratio to convert the operation amount of an operating member based on the actual steering amount (hereinafter, sometimes referred to as a "converted operation amount"), and to control the operation reaction force based on the difference between the converted operation amount and the actual operation amount (hereinafter, sometimes referred to as an "operation amount deviation"). In such a control of the operation reaction force, grasping an appropriate converted operation amount is the key to applying an appropriate operation reaction force, and applying an appropriate operation reaction force makes it possible to improve the practicality of the steer-by-wire system. The present invention has been made in consideration of such a situation, and an object of the present invention is to provide a steer-by-wire type steering system that is highly practical. [Means for solving the problem]

[0005] In order to solve the above problems, the steering system of the present invention comprises: A steer-by-wire type steering system equipped in a vehicle, the system comprising: an operating member operated by a driver; a reaction force imparting device that imparts an operation reaction force to the operating member; a steering device that steers wheels; and a controller that controls the reaction force imparting device and the steering device, The controller: Every moment, a steering control unit that determines a steering gear ratio and controls the steering device so that a ratio of a steering amount of the wheels to an operation amount of the operation member becomes the steering gear ratio; Every moment, a converted operation amount determination unit that determines a converted operation amount by converting an actual steering amount of the wheels into an operation amount of the operation member based on the reciprocal of the determined steering gear ratio; Every moment, a reaction force control unit that controls the reaction force application device based on an operation amount deviation, which is a difference between an actual operation amount of the operating member and the converted operation amount, so that the larger the operation amount deviation, the larger the operation reaction force becomes; having The converted manipulated variable determination unit Steering gear ratio to be determined When a steering state change signal indicating a sudden change in the steering state is input to the controller, the steering state change signal is input to the controller.The difference in the conversion operation amount, Immediately after that point Based on the steering gear ratio, the difference in the amount of steering of the wheels is converted into a converted steering amount offset value, and from that point on, the converted steering amount offset value is gradually decreased. To be determined The converted manipulated variable correction value is determined by reconverting the converted manipulated variable into a difference based on the reciprocal of the steering gear ratio, and the converted manipulated variable is corrected by the converted manipulated variable correction value. Effect of the Invention

[0006] In steer-by-wire systems, the steering gear ratio is generally variable, but when the steering gear ratio suddenly changes, if the steering of the actual wheels does not follow the operation of the operating member, or if the sudden change in the steering amount of the actual wheels is actively suppressed, it may be difficult to grasp the appropriate converted operation amount. In the steer-by-wire system of the present invention, when the steering gear ratio suddenly changes, the converted operation amount determination unit executes the above-mentioned conversion operation amount correction process, so that an appropriate converted operation amount can be obtained even when the steering gear ratio suddenly changes, and as a result, an appropriate operation reaction force is applied to the operating member. Therefore, according to the present invention, a highly practical steering system is realized. Aspects of the Invention

[0007] The "operating member" in the steering system of the present invention is generally something like a steering wheel, but may also be something like a joystick. The "reaction force applying device" may be, for example, one having an electric motor as a drive source, and configured to apply a biasing force to the operating member by the force of the electric motor. The "steering device" may be, for example, one having an electric motor as a drive source, and configured to steer the wheels by the force of the electric motor. It may also be one having a configuration in which the wheels are steered by the hydraulic pressure of a hydraulic fluid.

[0008] When the operating member is a steering wheel, the "operation amount" of the operating member can be considered to be the operation angle of the steering wheel, or more specifically, the rotation angle from the posture when the vehicle is moving straight ahead. The "steering amount" of the wheels can be various, such as the turning angle (toe angle displacement) from the direction of the wheels when the vehicle is moving straight ahead, the amount of left / right displacement of a rod connecting the left and right wheels from its neutral position (the position when the vehicle is moving straight ahead) when the steering device has a rod, and the rotation angle of the pinion from its rotation position when the vehicle is moving straight ahead when the steering device has a pinion that meshes with the rod.

[0009] The controller may be configured to include a computer, ASIC, etc., and drive circuits (drivers) for the drive sources of the reaction force application device and the steering device. The "steering control unit," "reaction force control unit," and "converted operation amount determination unit" of the controller are functional units realized by calculation processing. The controller may be configured with all of these functional units as one unit, or may be configured with multiple units each including several functional units.

[0010] The "steering control unit" can be configured to determine a target steering amount, which is the amount of steering of the wheels to be realized, based on the actual operation amount of the operating member and the steering gear ratio, and control the steering device so that the actual steering amount of the wheels becomes the target steering amount. The steering system of the present invention may be configured to make the "steering gear ratio (hereinafter, sometimes simply referred to as "gear ratio") variable. In other words, the steering system may be a so-called VGRS (variable gear ratio system). In that case, for example, the steering control unit may be configured to have a gear ratio determination unit that determines the gear ratio based on the operation amount of the operating member and the traveling speed of the vehicle (hereinafter, sometimes referred to as "vehicle speed"). In the case where the gear ratio is changed based on the vehicle speed, for example, when the controller is unable to recognize the vehicle speed due to a defect in the vehicle speed sensor, the controller can determine that the gear ratio has changed suddenly.

[0011] The "reaction force control unit" may be configured to determine an operation reaction force to be applied by combining a plurality of components, and to control the reaction force application device based on the determined operation reaction force. The plurality of components may be, for example, an "assist component" for assisting the operation of the operating member by the driver, a "steerage load dependent component" based on the load of the steering device with respect to the steering of the wheels, and an "operation amount deviation dependent component" based on the above-mentioned operation amount deviation. The "operation amount deviation" is recognized as the difference between the actual operation amount of the operating member and the above-mentioned converted operation amount, as described above, in order to grasp the deviation between the operation amount of the operating member and the steering amount of the wheels. For example, the deviation of the converted operation amount from the actual operation amount may be recognized as the operation amount deviation. The reaction force control unit controls the reaction force application device so that the larger the operation amount deviation, the larger the operation reaction force, that is, the larger the operation amount deviation dependent component, for the purpose of suppressing the operation of the operating member when the steering of the wheels does not follow the operation of the operating member, or for the purpose of making the driver recognize that the steering of the wheels does not follow.

[0012] In order to identify the operation amount deviation, the "converted operation amount determination unit" determines the "converted operation amount" by converting the actual wheel steering amount into the operation amount of the operating member based on the reciprocal of the gear ratio (hereinafter, sometimes referred to as the "reverse gear ratio") as described above. A sudden change in the gear ratio also causes a sudden change in the reverse gear ratio, resulting in a disparity in the converted operation amount, that is, a gap in the operation amount deviation. In order to prevent a sudden change in the operation reaction force due to the gap occurring in the operation amount deviation, the converted operation amount determination unit corrects the converted operation amount by the "converted operation amount correction value", thereby gradually changing the converted operation amount. Therefore, the converted operation amount correction value is determined as described above. The determination of this converted operation amount correction value will be described in detail later.

[0013] When the steering control section is configured to determine the target steering amount as described above, a sudden change in the gear ratio will also cause a gap in the determined target steering amount. In view of this, it is desirable that the steering control section, when the gear ratio suddenly changes, grasps the difference in the target steering amount occurring at the time of the sudden change as a target steering amount offset value, and determines a target steering amount correction value by gradually decreasing the target steering amount offset value from that point onwards, and corrects the target steering amount by this correction. When such a correction process for the target steering amount is performed, it is desirable to gradually decrease the converted steering amount offset value in accordance with the gradual decrease in the target steering amount offset value by the steering control section. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating a hardware configuration of a steering system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing a functional configuration of a controller provided in the steering system of the embodiment. [Diagram 3] 4 is a graph showing a steering gear ratio determination map used for determining a steering gear ratio in the steering system of the embodiment. [Figure 4] 4 is a block diagram showing a functional configuration of a target steering angle determination unit of a controller included in the steering system of the embodiment. FIG. [Diagram 5] 4 is a block diagram showing a functional configuration of a converted operation angle determination unit of a controller provided in the steering system of the embodiment. FIG. [Figure 6] 6 is a block diagram showing a functional configuration of a release angular velocity adjustment unit included in the converted operation angle determination unit shown in the block diagram of FIG. 5. [Figure 7] 7 is a block diagram showing a functional configuration of another converted operating angle determiner, which is a comparative example of the converted operating angle determiner shown in the block diagram of FIG. 5. [Figure 8] 8 is a table for explaining a difference between the converted operating angle determination processes of the two converted operating angle determination units whose block diagrams are respectively shown in FIG. 5 and FIG. 7. [Figure 9]7 is a block diagram showing a functional configuration of yet another converted operating angle determination unit serving as a comparative example to the converted operating angle determination unit shown in the block diagram of FIG. 5. [Figure 10] 10 is a table for explaining a difference between the converted operating angle determination processes of the two converted operating angle determination units whose block diagrams are respectively shown in FIG. 5 and FIG. 9 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A steer-by-wire type steering system according to an embodiment of the present invention will be described in detail below with reference to the drawings. In addition to the following embodiment, the present invention can be embodied in various forms including those described in the above section on "Modes of the Invention" and various modifications and improvements based on the knowledge of those skilled in the art. EXAMPLES

[0016] [A] Steering system hardware configuration The steering system of the embodiment is a steer-by-wire type steering system, as shown diagrammatically in FIG. 1, and is roughly composed of an operation section 14 having a steering wheel 10 which is an operating member operated by the driver and a reaction force actuator 12 which acts as a reaction force application device for applying an operation reaction force to the steering wheel 10, a steering section 20 which has a steering actuator 18 which acts as a steering device for steering the wheels 16, and a steering electronic control unit (hereinafter sometimes abbreviated as "steering ECU") 22 which acts as a controller which controls the reaction force actuator 12 and the steering actuator 18.

[0017] Regarding the operation unit 14, the steering wheel 10 is fixed to the tip of the steering shaft 30, and the reaction force actuator 12 has a reaction force motor 32, which is an electric motor as a power source, and a reduction mechanism 38 consisting of a worm 34 and a worm wheel 36 attached to the motor shaft of the reaction force motor 32, and the worm wheel 36 is attached to the steering shaft 30. The reaction force actuator 12 generates a reaction force torque Tq that depends on the motor torque of the reaction force motor 32. C Generates a reaction torque Tq C is applied to the steering wheel 10 as a reaction force against the operation of the steering wheel 10.

[0018] The reaction motor 32 is a three-phase brushless motor, and the rotation phase of the motor shaft of the reaction motor 32, or simply the rotation angle of the reaction motor 32 (hereinafter sometimes referred to as the “reaction motor rotation angle”) θ MC The steering shaft 30 has a structure in which two shaft portions, an upper portion and a lower portion, are connected via a torsion bar 42, and the operation unit 14 detects the amount of twist of the torsion bar 42 to thereby determine the operation torque Tq applied to the steering wheel 10 by the driver. O The operation torque sensor 44 detects the reaction force motor rotation angle θ (which is a sub-concept of “operation force”). MC and the operation torque Tq detected by the operation torque sensor 44 O A signal regarding the above is sent to the steering ECU 22.

[0019] Regarding the steering section 20, the steering actuator 18 has a steering rod 50 extending left and right, and a housing 52 that holds the steering rod 50 so that it can move left and right. A screw groove 54 constituting a ball screw mechanism is formed in the steering rod 50, and a nut 56 that holds a bearing ball is held in the housing 52 so as to be rotatable but immovable left and right so as to screw into the screw groove 54. A steering motor 58, which is an electric motor serving as a drive source, is disposed in the housing 52, and a timing belt 62 is wound around a pulley 60 attached to a motor shaft of the steering motor 58 and the outer periphery of the nut 56 that functions as another pulley. The rotation of the motor shaft of the steering motor 58, i.e., the rotation of the steering motor 58, rotates the nut 56, and the steering rod 50 moves left and right. The left and right ends of the steering rod 50 are connected, via ring rods (not shown), to knuckle arms of steering knuckles that rotatably hold the left and right wheels 16. As the steering rod 50 moves left and right, the left and right wheels 16 are turned, i.e., steered.

[0020] A rack 64 is formed on the steering rod 50, and a pinion shaft 66 is rotatably held in the housing 52 in a state of meshing with the rack 64. The rack 64 and the pinion shaft 66 do not necessarily have to be provided in the steering actuator 18 constituting the present steer-by-wire type steering system. As is easily understood, by connecting the pinion shaft 66 to the steering shaft 30 of the operation unit 14, a general power steering system is realized. In other words, the present steering system is constructed by slightly modifying the structure of a general power steering system. The steering rod 50 can also be called a rack bar, since the rack 64 is formed on the steering rod 50.

[0021] The steering motor 58 is a three-phase brushless motor, and the rotation phase of the motor shaft of the steering motor 58, or simply, the rotation angle of the steering motor 58 (hereinafter sometimes referred to as the "steering motor rotation angle") θ MSThe motor rotation angle sensor 68 detects the steering motor rotation angle θ MS The signal is sent to the steering ECU 22.

[0022] The steering ECU 22 is configured to include a computer constituted by a CPU, ROM, RAM, etc., an inverter which is a drive circuit for the reaction force motor 32, and an inverter which is a drive circuit for the steering motor 58. The steering ECU 22 obtains a signal relating to the vehicle speed v from a vehicle speed sensor 72 which detects the traveling speed v of the vehicle (hereinafter sometimes abbreviated as "vehicle speed")

[0023] [B] Controller Functions The steering ECU 22, which is the controller of this steering system, has a functional configuration as shown in the functional block diagram in Fig. 2. This functional configuration is realized by a computer executing a predetermined program, but may also be realized by a dedicated circuit such as an ASIC. Incidentally, the steering ECU 22 executes various processes at a control cycle with a relatively short time pitch (for example, several msec to several tens of msec, which may also be called a "control pitch").

[0024] The steering ECU 22 can be roughly divided into a reaction force control section 100, a turning control section 102, and a converted operation angle determination section 104 as a converted operation amount determination section. Reaction force control section 100, turning control section 102, and converted operation angle determination section 104 will each be described in detail below.

[0025] Note that most of what is input to or output from each component shown in the figure are signals indicating values ​​such as torque, its components, steering angle, and operation angle, but in consideration of the redundancy of the explanation, in the following explanation, it will be expressed simply as torque, its components, steering angle, operation angle, etc. being input to or output from each component. Also, the operation angle and steering angle described later will be treated as having a positive value when shifted to the left or right, and a negative value when shifted to the other side, with the neutral position being 0, and the absolute value becoming larger when the shift amount from the neutral position is large. Various parameters related to the operation angle and steering angle will be treated in the same manner.

[0026] (a) Reaction force control section The reaction force control unit 100 calculates the reaction torque Tq by the reaction force actuator 12. C (which is a sub-concept of "operation reaction force"), and each of them controls the reaction torque Tq C The assist component Tq C-A , steering load dependent component Tq C-L The control angle deviation dependent component Tq C-O The system includes an assist component determiner 106, a steering load dependent component determiner 108, and an operation angle error dependent component determiner 110 which determine the above components, respectively.

[0027] In the control of the present steering system, the operation angle θ of the steering wheel 10 is used as the operation amount of the operation member. O is used, the reaction force control unit 100 detects the reaction force motor rotation angle θ MC The operation angle θ O The operation angle conversion unit 112 converts the operation angle θ O and reaction motor rotation angle θ MC Since the integrated amount of the steering wheel 10 is related to the reduction ratio of the reduction mechanism 38, the conversion is performed based on the reduction ratio. Although a detailed explanation is omitted, the steering system of the present invention is configured such that the steering wheel 10 is rotated at an operating angle θ OThe operation angle conversion unit 112 converts the operation angle θ based on the detection value of the sensor (not shown). O The calibration is performed at a predetermined timing.

[0028] The reaction torque Tq mentioned above C The determination of each component is explained in order: Assist component Tq C-A is a component similar to the assist force in so-called power steering, and the assist component determination unit 106 determines the operation torque Tq detected by the operation torque sensor 44. O , the assist component Tq based on the vehicle speed v detected by the vehicle speed sensor 72 C-A Simply put, the operating torque Tq O The larger the value, the larger the assist component Tq is determined to be. When the vehicle speed v is high, the assist component Tq is set to a small value in order to make the driver's feeling of operation of the steering wheel 10 (hereinafter, sometimes referred to as "steering operation feeling" or simply "operation feeling") heavier. When the vehicle speed v is low, the assist component Tq is set to a large value in order to make the driver's feeling of operation lighter. C-A The direction of the steering wheel 10 is the same as the steering operation direction.

[0029] Steering load dependent component Tq C-L is the reaction torque Tq C It can be considered as a central component, and roughly speaking, it is a component that allows the driver to feel the steering force, which is the force required to steer the wheels 16. It can also be considered as a component based on the force (axial force) acting on the steering rod 50 of the steering actuator 18 in its axial direction, and is a component that allows the driver to feel not only the above-mentioned steering force, but also a wide range of forces acting on the wheels 16 from the road surface.

[0030] In detail, the steering load dependent component Tq C-Lincludes a theoretical component that is a theoretical component based on the steering angle θ of the wheels 16 and the vehicle speed v, and an actual load dependent component based on the actual load of the steering actuator 18, and the steering load dependent component determination unit 108 determines these components and adds up the determined components to determine the steering load dependent component Tq C-L Determine the steering load dependent component Tq C-L The direction of is opposite to the steering direction.

[0031] The theoretical component is a component that does not take into account friction between the road surface and the wheels 16, and can be considered as a component that takes into account the self-aligning torque of the wheels 16. Specifically, the steering angle θ at which the wheels 16 should be steered is S The target steering angle θ S * Based on the vehicle speed v detected by the vehicle speed sensor 72 and the self-aligning torque of the wheels 16, the target steering angle θ S * The actual load dependent component is determined to be a larger value as the load of the steering actuator 18 is larger and the vehicle speed v is higher. S Since the steering current I S Based on this, the steering current I S The larger the value, the larger the value is determined.

[0032] Control angle deviation dependent component Tq C-O is the steering angle θ of the steering wheel 10 O The steering angle θ of the wheel 16 with respect to S In detail, the difference in the operating angle θ O and steering angle θ SThis component takes into consideration the deviation of the relationship between the steering torque and the steering angle from the relationship corresponding to the steering gear ratio γ (hereinafter, sometimes simply referred to as "gear ratio γ"). For example, when the wheels 16 hit a steering barrier such as a curb or a ditch, or when the power supply from the power source to the steering motor 58 is limited in order to protect the steering actuator 18, etc., there is a risk that the steering of the wheels 16 will not follow the steering operation. When the deviation is large, the reaction torque Tq C Therefore, in the present steering system, the actual steering angle θ S The operating angle θ is calculated by the inverse of the gear ratio γ (hereinafter sometimes referred to as "inverse gear ratio 1 / γ"). O The converted angle is the converted operating angle θ'. O (a type of converted manipulated variable), and the manipulated variable deviation dependent component determiner 110 determines the converted manipulated variable θ' O and the actual operation angle θ input from the operation angle conversion unit 112 O The difference between the operating angle deviation Δθ O The larger the control angle deviation dependent component Tq C-O By the way, the control angle deviation dependent component Tq C-O The direction of the steering load dependent component Tq C-L The converted steering angle θ' is opposite to the steering direction. O is determined by the converted operating angle determination unit 104, and the process of this determination, that is, the functional configuration of the converted operating angle determination unit 104 will be described in detail later.

[0033] The assist component Tq determined by the assist component determination unit 106 C-A , the turning load dependent component Tq determined by the turning load dependent component determination unit 108 C-L , the operation angle deviation dependent component Tq as the operation amount deviation dependent component determining unit C-O The control angle deviation dependent component Tq determined by 110 C-O is input to an adder / subtractor 114, and the reaction torque Tq to be applied is C is determined.

[0034] The reaction torque Tq output from the adder / subtractor 114 C is input to the reaction force current control unit 116. The reaction force current control unit 116 is configured to include an inverter that is a drive circuit (driver) of the reaction force motor 32. The reaction force current control unit 116 calculates the reaction force torque Tq C Based on this, the reaction current I C Determine the reaction current I C is supplied to the reaction motor 32 from the inverter.

[0035] (b) Steering control section The steering control unit 102 controls the steering angle θ of the wheels 16 which are steered by the steering actuator 18 which is a steering device. S and has a gear ratio determination section 120, a target steering angle determination section 122, a steering torque determination section 124, and a steering current control section 126.

[0036] In the control of this steering system, the amount of steering of the wheels 16 is determined by the steering angle θ S is used, the steering control unit 102 detects the steering motor rotation angle θ MS The steering angle θ S Incidentally, the steering angle θ S Alternatively, the toe angle of the wheels 16 may be used, but in the control of the present steering system, the rotation angle of the pinion shaft 66 is used. S and the steering motor rotation angle θ MS Since the integrated amount of is in a relationship corresponding to a predetermined reduction gear ratio, specifically, a reduction gear ratio determined by the reducer included in steering motor 58, the lead angle of the ball screw mechanism of steering actuator 18, the diameter of pinion shaft 66, etc., conversion is performed based on that reduction gear ratio. Although detailed explanation is omitted, this steering system has a sensor (not shown) for detecting the rotation angle from the rotation position of pinion shaft 66 when wheels 16 are in a straight traveling state, and based on the detection value of that sensor, steering angle θ S The calibration is performed at a predetermined timing.

[0037] The gear ratio determination unit 120 converts the actual operation angle θ O Based on the vehicle speed v detected by the vehicle speed sensor 72 and the steering gear ratio determination map shown in the form of a graph in FIG. 3 (hereinafter, simply referred to as the "gear ratio determination map"), the gear ratio γ is determined. O The steering angle θ S is the ratio of γ=θ S / θ O According to the gear ratio determination map of Fig. 3, the gear ratio γ is determined to be a smaller value as the vehicle speed v increases, and conversely, the gear ratio γ is determined to be a larger value as the vehicle speed v decreases, thereby improving the steering stability when the vehicle speed v is high and improving the turning performance when the vehicle speed v is low. In particular, the steering angle θ when the vehicle speed v is high O In the gear ratio determination map of FIG. 3, the thick line (indicated by ☆) indicates the operation angle θ to be adopted when the vehicle speed v information cannot be obtained due to a malfunction of the vehicle speed sensor 72, that is, when the vehicle speed is in an invalid state. O and the gear ratio γ (hereinafter, may be referred to as the “vehicle speed invalid state relationship line”), and in the vehicle speed invalid state, the gear ratio γ is determined by referring to this line. The gear ratio γ determined by the gear ratio determination unit 120 is sent to the target steering angle determination unit 122 and the converted operation angle determination unit 104.

[0038] In simple terms, the target steering angle determination unit 122 determines the operation angle θ O and the gear ratio γ determined by the gear ratio determination unit 120, the steering angle θ of the wheels 16 is determined. S The target steering angle θ S * (which is a type of target steering amount) is determined. The determined target steering angle θ S * is sent to the steering torque determination unit 124 and the steering load dependent component determination unit 108 of the reaction force control unit 100.S * The process of determining this, that is, the functional configuration of target steering angle determination unit 122 will be described in detail later.

[0039] The steering torque determination unit 124 determines the steering torque Tq required to steer the wheels 16. S This is a functional part that determines the steering torque Tq (a type of steering force). S can be considered to be, for example, the torque generated by the steering motor 58. Specifically, the steering torque determination unit 124 calculates the actual steering angle θ S and the target steering angle θ determined by the target steering angle determination unit 122. S * Based on this, the target steering angle θ S * The steering angle θ S The deviation of the steering angle Δθ S and the steering angle deviation Δθ S Based on this, the steering torque Tq S The method of following this feedback control law is a common one, and the description thereof will be omitted here.

[0040] The steering current control unit 126 is configured to include an inverter that is a drive circuit (driver) of the steering motor 58. The steering current control unit 126 determines the steering torque Tq determined by the steering torque determination unit 124. S Based on this, the steering current I S Determine the steering current I S is supplied from the inverter to the steering motor 58. The steering ECU 22 controls the steering current I S The steering wheel has a current sensor 130 for detecting the steering current I S is the steering load dependent component Tq C-L The result is sent to the steering load dependent component determiner 108 of the reaction force control unit 100 to be used in determining the steering load dependent component.

[0041] The target turning angle determination unit 122 has a functional configuration as shown in the functional block diagram of Fig. 4. The target turning angle determination unit 122 has a multiplier 132, which receives the operation angle θ of the steering wheel 10 from the operation angle conversion unit 112. O The gear ratio γ is input from the gear ratio determination unit 120. The multiplier 132 multiplies the operation angles θ O By multiplying this by the gear ratio γ, the target steering angle θ * S The basic target steering angle θ * S-B Determine.

[0042] Basic target steering angle θ * S-B is input to an adder-subtracter 134. The adder-subtracter 134 also inputs a target steering angle correction value θ * S-C (a type of target turning amount correction value) is also input, and an adder / subtractor 134 calculates a basic target turning angle θ * S-B The target steering angle correction value θ * S-C The target steering angle θ * S is determined.

[0043] The target steering angle determination unit 122 has a gradual decrease processing unit 136, and the gradual decrease processing unit 136 determines the target steering angle correction value θ * S-C The gradual reduction processing unit 136 determines whether the basic target steering angle θ * S-B In other words, when the basic target steering angle θ * S-B When the steering angle θ changes relatively large in a stepwise manner, the target steering angle θ * S In order to gradually change the target steering angle correction value θ * S-C Determine.

[0044] More specifically, the target steering angle determination unit 122 includes an adder / subtractor 138 and a previous value memory 140, and determines the basic target steering angle θ * S-B and the target steering angle θ in the previous control cycle. * S The target steering angle difference Δθ * (which is a type of target turning amount difference) is input to gradual reduction processing section 136. On the other hand, a steering state change signal SCS is input to gradual reduction processing section 136 when a situation occurs in which the gear ratio γ changes suddenly. Gradual reduction processing section 136 calculates the target turning angle difference Δθ at the time when this steering state change signal SCS is input, i.e., at the time when the gear ratio γ changes suddenly. * The target steering angle offset value θ * SO Then, in the subsequent control cycles, the gradual reduction processing unit 136 grasps the target steering angle offset value θ * SO The upper limit dθ * SO-UG ,Lower limit dθ * SO-LG The target steering angle offset value θ is gradually decreased to 0 at an angular velocity that does not exceed θ . In other words, the offset release process is performed. * SO is the change rate limit value (guard value) when approaching 0, and the lower limit is the target steering angle offset value θ * SO is a change rate limit value when approaching 0. The gradual decrease processing unit 136 gradually decreases the target steering angle offset value θ * SO The target steering offset residual angle θ * SO-RE This target steering offset remaining angle θ * SO-RE is the target steering angle correction value θ * S-C In addition, the target steering offset remaining angle θ * SO-REis also output to the converted operation angle determination unit 104, and the target turning angle offset value θ * SO The offset release angular velocity dθ is the angular velocity at which * SO is also output to the converted operating angle determination unit 104.

[0045] (c) Conversion operation angle determination section The converted operation angle determination unit 104 has a functional configuration as shown in the functional block diagram of Fig. 5. The converted operation angle determination unit 104 has a multiplier 150, which receives the actual steering angle θ of the wheels 16 from the steering angle conversion unit 128 of the steering control unit 102. S On the other hand, the gear ratio γ is input to the converted operation angle determination unit 104 from the gear ratio determination unit 120, and the gear ratio γ is converted to an inverse gear ratio 1 / γ, which is the inverse of the gear ratio γ, by a reciprocal converter 152. This inverse gear ratio 1 / γ is also input to the multiplier 150. The multiplier 150 multiplies the steering angle θ S By multiplying this by the reverse gear ratio 1 / γ, the converted operating angle θ' is obtained. O The basic conversion angle θ' that is the basis of O-B Determine.

[0046] Basic conversion operating angle θ' O-B is input to an adder-subtracter 154. The adder-subtracter 154 also receives a converted operation angle correction value θ′ O-C (a kind of converted operation amount correction value) is also input, and in the adder / subtracter 154, the basic converted operation angle θ' O-B Conversion angle correction value θ' O-C The converted operating angle θ' is obtained by O is determined.

[0047] Similarly to the target steering angle determination unit 122, the converted operating angle determination unit 104 also determines the converted operating angle θ' due to a sudden change in the reverse gear ratio 1 / γ caused by a sudden change in the gear ratio γ. O In other words, when the converted operating angle θ' O When the reaction torque Tq changes in a relatively large step C In order to prevent sudden changes in the operation angle deviation dependent component TqC-O To prevent a sudden change in the converted operating angle θ' O Specifically, converted operation angle determination section 104 also executes an offset release process similar to that of target turning angle determination section 122.

[0048] In order to execute the offset release process, the converted operation angle determination unit 104 also has a gradual reduction processing unit 156 similar to the target steering angle determination unit 122. The gradual reduction processing unit 156 reduces the converted operation angle correction value θ′ O-C The converted steering offset residual angle θ' that is the basis of SO-RE (see below) will be determined.

[0049] More specifically, the converted operating angle determination unit 104 includes an adder / subtractor 158 and a previous value memory 160, and determines the basic converted operating angle θ' in the current control cycle. O-B and the converted operation angle θ' in the previous control cycle. O The difference between the converted operating angle Δθ' and O (This is a kind of converted operation amount difference) is determined. O and the gear ratio γ are input to a multiplier 162, which multiplies them together to obtain a converted operating angle difference Δθ′ O is the steering angle θ S The converted steering angle difference Δθ' S (This is a kind of converted steering angle difference.) S is input to the gradual decrease processing unit 156. On the other hand, the above-mentioned steering state change signal SCS is also input to the gradual decrease processing unit 156, and the gradual decrease processing unit 156 calculates the converted steering angle difference Δθ′ at the time when the steering state change signal SCS is input, that is, at the time when the gear ratio γ changes suddenly. S Convert the steering angle offset value θ' SO Then, in the subsequent control cycles, gradual decrease processing unit 156, like gradual decrease processing unit 136, grasps the converted steering angle offset value θ' SO The upper limit value dθ' SO-UG ,Lower limit dθ' SO-LGThe gradual decrease processing unit 156 gradually decreases the converted steering angle offset value θ' to 0 at an angular velocity not exceeding θ' every time a control cycle progresses. SO The above-mentioned converted steering offset residual angle θ' SO-RE The reciprocal converter 152 also inputs the inverse gear ratio 1 / γ to the multiplier 163, and the multiplier 163 outputs the converted steering offset residual angle θ′ SO-RE By multiplying this by the reverse gear ratio 1 / γ, the converted operating angle correction value θ' is obtained. O-C and outputs it to the adder / subtractor 154. In simple terms, the converted operating angle determiner 104 simply determines the converted operating angle θ' O Instead of performing offset release processing for the converted operating angle θ' O The steering angle θ' is converted once by the gear ratio γ. S (a type of converted steering angle) and convert it to the converted steering angle θ' S The offset release process is performed on the converted steering angle θ′ S Then, convert the operating angle θ' by the reverse gear ratio 1 / γ. O The process involves converting the

[0050] In the converted operation angle determination unit 104, the upper limit value dθ′ in the gradual decrease processing unit 156 is SO-UG ,Lower limit dθ' SO-LG is the converted steering angle θ' S The speed of the offset release process relative to the offset release angular velocity dθ' SO The target steering angle θ * Offset release angular velocity dθ * SO More specifically, the converted operation angle determination unit 104 has a release angular velocity adjustment unit 164, and the gradual reduction processing unit 156 reduces the offset release angular velocity dθ′ determined by the release angular velocity adjustment unit 164. SO The upper limit value dθ' SO-UG and set the offset release angular velocity dθ' SO The sign of this is inverted by an inverter 166 (-dθ' SO) to the lower limit dθ' SO-LG is set to.

[0051] The process by release angular velocity adjustment unit 164 will be described. Release angular velocity adjustment unit 164 has a functional configuration as shown in the functional block diagram of Fig. 6. Release angular velocity adjustment unit 164 receives target turning offset remaining angle θ * SO-RE is input, and the converted steering offset remaining angle θ' determined by the gradual reduction processing unit 156 is SO-RE The target steering offset residual angle θ * SO-RE , Equivalent steering offset residual angle θ' SO-RE are input to an absolute value generator 168 and an absolute value generator 170, respectively, to calculate a target steering offset remaining angle θ * SO-RE Absolute value of |θ * SO-RE |, Equivalent steering offset residual angle θ' SO-RE Absolute value of |θ' SO-RE | is obtained, and the difference between them, the offset residual angle difference Δθ SOR The release angular velocity adjustment unit 164 has a gain determination unit 174, and the adjustment gain G is determined in the gain determination unit 174. The adjustment gain G is calculated by S The speed of the offset release process for the target steering angle θ * Offset release angular velocity dθ * SO As shown in the figure, the offset residual angle difference Δθ SOR is close to 0, it is determined to be 1, and the target steering offset remaining angle θ * SO-RE is the converted steering offset remaining angle θ' SO-RE When the converted steering angle θ' is larger than the S In order to make the offset release process faster, the offset residual angle difference Δθ SOR The larger the value, the larger the target steering offset residual angle θ * SO-RE is the converted steering offset remaining angle θ'SO-RE If the converted steering angle θ' is smaller than S In order to slow down the offset release process for SOR The larger the absolute value of the adjustment gain G is, the smaller the value is determined. The adjustment gain G determined by the gain determination unit 174 is input to a multiplier 176. The multiplier 176 receives the target steering angle θ * S Offset release angular velocity dθ * SO are input from the target steering angle determination unit 122, and the offset release angular velocity dθ * SO and an adjustment gain G are multiplied by a multiplier 176 to obtain an offset release angular velocity dθ′ SO is determined.

[0052] [C] Equivalent operating angle determined when the gear ratio suddenly changes As described above, the converted operating angle determination unit 104 determines the converted operating angle θ′ O In determining the converted operating angle θ of the steering wheel 10, the correction process described above, that is, the correction process using the converted operating angle correction value, is performed. The determination of the converted operating angle by the converted operating angle determination unit 104 when the gear ratio γ changes suddenly will be described below, in comparison with the determination by another convertible operating angle determination unit that can be used. O Consider the case where the vehicle speed becomes invalid when the angle is 100 deg, and the gear ratio γ suddenly changes from 4.0 to 2.0.

[0053] (a) What to do when the wheels do not follow the steering operation Instead of the above-mentioned converted operating angle determination unit 104, for example, a converted operating angle determination unit 180 having a functional configuration as shown in a block diagram in FIG. 7 may be adopted. This converted operating angle determination unit 180 has an adder-subtracter 182, a reciprocal converter 184, and a multiplier 186. The adder-subtracter 182 receives the actual steering angle θ S and the target turning offset remaining angle θ from the gradual decrease processing unit 136 of the target turning angle determination unit 122. * SO-REare input, and are added together in an adder / subtractor 182 to obtain the offset steering angle θ S-O In the reciprocal converter 184, the gear ratio γ input from the gear ratio determination unit 120 is converted to an inverse gear ratio 1 / γ, and the inverse gear ratio 1 / γ and the offset steering angle θ S-O and are multiplied to obtain the converted operating angle θ' O is determined.

[0054] As shown in the table of FIG. 8(a), when the turning of the wheels 16 sufficiently follows the steering operation, the turning angle θ S is 400deg, gear ratio γ is 4.0, target steering offset residual angle θ * SO-RE is 0 deg, and according to the converted operation angle determination unit 180, the offset turning angle θ S-O is 400deg, and the converted operating angle θ' O Immediately after the vehicle speed is invalid, the steering angle θ S does not change, and the input gear ratio γ suddenly changes to 2.0, but the target steering offset remaining angle θ * SO-RE As a result, the offset steering angle θ S-O is 200deg, and the converted operating angle θ' O In this way, when the turning of the wheels 16 sufficiently follows the steering operation, even if the gear ratio γ changes suddenly, the converted operation angle θ' O remains unchanged.

[0055] Consider a case where the wheel 16 hits a curb or the like and the turning of the wheel 16 does not follow the steering operation. Specifically, the operation angle is 100 deg, but the turning angle θ S Consider the case where the steering angle θ reaches only 300 deg. S is 300deg, gear ratio γ is 4.0, target steering offset residual angle θ * SO-RE is 0 deg, and according to the converted operation angle determination unit 180, the offset turning angle θ S-O is 300deg, and the converted operating angle θ'O Immediately after the vehicle speed is invalid, the steering angle θ S does not change, and the input gear ratio γ suddenly changes to 2.0, but the target steering offset remaining angle θ * SO-RE As a result, the offset steering angle θ S-O is 100deg, and the converted operating angle θ' O In this way, when the turning of the wheels 16 does not follow the steering operation, the converted operation angle θ' O This sudden change causes the reaction force to change as well.

[0056] According to the conversion operation angle determination unit 104 in the steering system of the embodiment, as shown in the table of FIG. 8(b), when the turning of the wheels 16 sufficiently follows the steering operation, the gear ratio γ is 4.0 and the turning angle θ is 1.0 immediately before the vehicle speed is invalidated. S is 400deg, basic conversion angle θ' O-B is 100 deg, and the converted operating angle difference Δθ' O ,Converted steering angle difference Δθ' S , Equivalent steering offset residual angle θ' SO-RE ,Converted operation angle correction value θ' O-C are both 0 deg, and the converted operating angle θ' O Immediately after the vehicle speed is invalid, the steering angle θ S does not change, and the gear ratio γ suddenly changes to 2.0, but the basic conversion operating angle θ' O-B is 200deg, the converted operating angle difference Δθ' O is 100deg, the converted steering angle difference Δθ' S is 200deg, equivalent steering offset remaining angle θ' SO-RE is 200deg, conversion operation angle correction value θ' O-C is 100deg, and the converted operating angle θ' O When the turning of the wheels 16 sufficiently follows the steering operation, even if the gear ratio γ changes suddenly, the converted operation angle θ' O remains unchanged.

[0057] On the other hand, as described above, the steering of the wheels 16 does not follow the steering angle θ S In this case, the steering angle θ S is 300deg, gear ratio γ is 4.0, basic conversion operating angle θ' O-B is 75 deg, and the converted operating angle difference Δθ' O ,Converted steering angle difference Δθ' S , Equivalent steering offset residual angle θ' SO-RE ,Converted operation angle correction value θ' O-C are both 0 deg, and the converted operating angle θ' O Immediately after the vehicle speed is invalid, the steering angle θ S Although the gear ratio γ suddenly changes to 2.0, the basic conversion operating angle θ' O-B is 150deg, the converted operating angle difference Δθ' O is 75deg, equivalent steering angle difference Δθ' S is 150deg, equivalent steering offset remaining angle θ' SO-RE is 150deg, conversion operation angle correction value θ' O-C is 75deg, and the converted operating angle θ' O According to the converted operation angle determination unit 104, even if the turning of the wheels 16 does not follow the steering operation, the converted operation angle θ′ due to a sudden change in the gear ratio γ is O In other words, the steering system of the embodiment deals with a sudden change in the gear ratio γ when the turning of the wheels 16 does not follow the steering operation.

[0058] (b) How to deal with the gear ratio fluctuation during offset release processing after a sudden gear ratio change In the target steering angle determination unit 122, the target steering angle offset value θ * SO is set, and as the control cycle proceeds, the target steering angle offset value θ * SOIn the steering system of this embodiment, the converted operation angle determination unit 104 also performs the offset release process after the gear ratio γ suddenly changes.

[0059] Converted operating angle θ' O In order to perform offset release processing relatively simply in determining the actual steering angle θ of the wheels 16, it is possible to employ a converted steering angle determination section 190 having a functional configuration as shown in a block diagram in FIG. 9. This converted steering angle determination section 190 has a multiplier 192, similar to the converted steering angle determination section 104. The multiplier 192 receives the actual steering angle θ of the wheels 16 from the steering angle conversion section 128 of the steering control section 102. S On the other hand, the gear ratio γ is input to the converted operation angle determination unit 190 from the gear ratio determination unit 120, and the gear ratio γ is converted to an inverse gear ratio 1 / γ, which is the inverse of the gear ratio γ, by a reciprocal converter 194. This inverse gear ratio 1 / γ is also input to a multiplier 192. The multiplier 192 multiplies the steering angle θ S By multiplying this by the reverse gear ratio 1 / γ, the converted operating angle θ' is obtained. O The basic conversion angle θ' that is the basis of O-B Determine.

[0060] The converted operating angle determination unit 190 has an adder / subtractor 196, similar to the converted operating angle determination unit 104, and determines the basic converted operating angle θ′ O-B is input to the adder-subtracter 196. The adder-subtracter 196 also receives a converted operation angle correction value θ' O-C is also input, and an adder / subtractor 196 calculates the basic converted operating angle θ' O-B The converted operation angle correction value θ' O-C The converted operating angle θ' is obtained by O is determined.

[0061] The converted steering angle determination unit 190 also has a gradual reduction processing unit 198 for executing the offset release process. The gradual reduction processing unit 198 outputs the converted steering offset residual angle θ′ SO-RE Instead, the converted operation angle correction value θ' O-C As a result, the converted operation offset residual angle θ′OO-RE will be output.

[0062] More specifically, the converted operating angle determination unit 190 includes an adder / subtractor 200 and a previous value memory 202, and determines the basic converted operating angle θ' in the current control cycle. O-B and the converted operation angle θ' in the previous control cycle. O The difference between the converted operating angle Δθ' and O (which is a kind of converted operation amount difference) is determined. In the converted operation angle determination unit 190, this converted operation angle difference Δθ' O is input as is to the gradual decrease processing unit 198. On the other hand, the above-mentioned steering state change signal SCS is also input to the gradual decrease processing unit 198, and the gradual decrease processing unit 198 calculates the converted operation angle difference Δθ′ at the time when this steering state change signal SCS is input, that is, at the time when the gear ratio γ suddenly changes. O Convert the operating angle offset value θ' OO Then, in the subsequent control cycles, the gradual reduction processing unit 198 grasps the converted operation angle offset value θ′ OO (a type of converted manipulated variable offset value) is set to the upper limit value dθ' OO-UG ,Lower limit dθ' OO-LG The gradual reduction processing unit 198 gradually reduces the converted operation angle offset value θ' to 0 at an angular velocity not exceeding θ' every time a control cycle progresses. OO The above-mentioned conversion operation offset residual angle θ' OO-RE to the adder / subtractor 196. In simple terms, the converted operating angle determination unit 190 differs from the converted operating angle determination unit 104 in that it simply determines the converted operating angle θ' O The offset release process is performed on the

[0063] The converted operation angle θ′ by the converted operation angle determination unit 190 accompanied by the offset release process O Let us consider the process of determining the steering angle θ of the steering wheel 10. O When the steering angle θ is 100 deg, the vehicle speed becomes invalid and the gear ratio γ changes suddenly from 4.0 to 2.0. After that, the steering wheel 10 is turned further and the steering angle θ OIt is also assumed that the turning of the wheels 16 sufficiently follows the steering operation.

[0064] According to the converted operation angle determination unit 190, as shown in the table of FIG. 10(a), immediately before the vehicle speed is invalid, the gear ratio γ is 4.0 and the steering angle θ S is 400deg, basic conversion angle θ' O-B is 100 deg, and the converted operating angle difference Δθ' O ,Converted operation offset residual angle θ' OO-RE That is, the converted operation angle correction value θ' O-C are both 0 deg, and the converted operating angle θ' O Immediately after the vehicle speed is invalid, the steering angle θ S does not change, and the gear ratio γ suddenly changes to 2.0, but the basic conversion operating angle θ' O-B is 200deg, the converted operating angle difference Δθ' O is 100deg, converted operation offset residual angle θ' OO-RE is 100 deg, that is, the converted operation angle correction value θ' O-C is 100deg, and the converted operating angle θ' O will output 100deg.

[0065] After that, the operation angle θ O Assuming that the gear ratio γ does not change during the offset release in which the offset has reached 105 deg, the target steering angle determination unit 122 determines the target steering offset remaining angle θ * SO-RE becomes 197 deg, and the target steering angle θ * S The steering angle θ S Accordingly, the converted operation angle determination unit 190 determines the basic converted operation angle θ' O-B becomes 203.5 deg, and assuming that the offset release processing in the conversion operation determination unit 190 proceeds in synchronization with the offset release processing by the target turning angle determination unit 122, the conversion operation offset remaining angle θ' OO-RE is 98.5 deg. As a result, the converted operating angle θ'O is the operation angle θ O The result is the same as above, 105 deg.

[0066] As can be seen from the gear ratio determination map of FIG. 3, more specifically, the vehicle speed invalid relation line indicated by a star on the map, even in the vehicle speed invalid state, the operation angle θ O The gear ratio γ changes depending on the offset release process. Therefore, it is necessary to take into consideration the change in the gear ratio γ during the offset release process.

[0067] According to the vehicle speed invalid time relationship line, during the offset release process, the operation angle θ O If the gear ratio γ changes from 2.0 to 2.05 when the steering angle shifts from 100 deg to 105 deg, the target steering offset remaining angle θ * SO-RE is 197 deg, but the gear ratio γ becomes 2.05, so the target steering angle θ * S The steering angle θ S The converted operation angle determination unit 190 determines the basic converted operation angle θ' O-B is 201.10deg, and the converted operation offset residual angle θ' OO-RE Since it is 98.5 deg, the converted operating angle θ' O is the operation angle θ O The result is 102.60 deg, which is different from the above.

[0068] Unlike the processing by the converted operation angle determination unit 190 described above, the converted operation angle determination unit 104 in the steering system of the embodiment calculates the converted operation angle θ′ in the following manner. O is determined.

[0069] According to the converted operation angle determination unit 104, as shown in the table of FIG. 10(b), immediately before the vehicle speed is invalid, the gear ratio γ is 4.0 and the steering angle θ S is 400deg, basic conversion angle θ' O-B is 100 deg, and the converted operating angle difference Δθ' O ,Converted steering angle difference Δθ'S , Equivalent steering offset residual angle θ' SO-RE ,Converted operation angle correction value θ' O-C are both 0 deg, and the converted operating angle θ' O Immediately after the vehicle speed is invalid, the steering angle θ S does not change, and the gear ratio γ suddenly changes to 2.0, but the basic conversion operating angle θ' O-B is 200deg, the converted operating angle difference Δθ' O is 100deg, the converted steering angle difference Δθ' S is 200deg, equivalent steering offset remaining angle θ' SO-RE is 200deg, conversion operation angle correction value θ' O-C is 100deg, and the converted operating angle θ' O will output 100deg.

[0070] During the offset release process, the operating angle θ O When the steering angle θ changes from 100° to 105°, if the gear ratio γ remains at 2.0, as described for the converted operation angle determination unit 190, S The converted operation angle determination unit 104 determines the basic converted operation angle θ' O-B becomes 203.5 deg, and assuming that the offset release processing in the conversion operation determination unit 104 proceeds in synchronization with the offset release processing by the target turning angle determination unit 122, the converted turning offset remaining angle θ' SO-RE is 197deg, conversion operation angle correction value θ' O-C is 98.5deg, and the converted operating angle θ' O As the operation angle θ O The same 105deg will be output.

[0071] During the offset release process, the operating angle θ O If the gear ratio γ changes from 2.0 to 2.05 when the steering angle θ changes from 100° to 105°, the steering angle θ S The converted operation angle determination unit 104 determines the basic converted operation angle θ' O-B is 201.10deg, and the converted steering offset remaining angle θ'SO-RE is 197deg, conversion operation angle correction value θ' O-C is 96.10deg, and the converted operating angle θ' O As the operation angle θ O The same 105deg will be output.

[0072] In this way, according to the converted operation angle determination unit 104, when the gear ratio γ suddenly changes and the steering operation proceeds with the offset release process thereafter, the appropriate converted operation angle θ′ is determined regardless of whether the gear ratio γ changes or not. O In other words, the converted operating angle determination unit 104 deals with the fluctuation of the gear ratio γ during the offset release process after the gear ratio γ suddenly changes. This is an advantage of the converted operating angle determination unit 104, and the advantage is that the converted operating angle determination unit 104 does not simply determine the converted operating angle θ' O Instead of performing offset release processing for the converted operating angle θ' O The steering angle θ' is converted once by the gear ratio γ. S and convert it into the converted steering angle θ' S The offset release process is performed on the converted steering angle θ′ S Then, convert the operating angle θ' by the reverse gear ratio 1 / γ. O This can be obtained by performing a process such as converting it into [Explanation of symbols]

[0073] 10: Steering wheel (operation member) 12: Reaction force actuator (reaction force application device) 16: Wheel 18: Steering actuator (steering device) 22: Steering electronic control unit (steering ECU) (controller) 32: Reaction force motor 40: Motor rotation angle sensor 44: Operation torque sensor 58: Steering motor 68: Motor rotation angle sensor 72: Vehicle speed sensor 100: Reaction force control unit 102: Steering control unit 104: Converted operation angle determination unit (converted operation amount determination unit) 120: Gear ratio determination unit 122: Target steering angle determination unit θ O :Operation angle [operation amount] θ' O : Converted operating angle [converted operating amount] θ' O-C:Converted operation angle correction value [Converted operation amount correction value] Δθ' O :Converted operating angle difference [Converted operating amount difference] Δθ O :Operation angle deviation [operation amount deviation] θ S :Steering angle [steering amount] θ * S :Target steering angle [target steering amount] θ * SO : Target steering angle offset value [Target steering amount offset value] Δθ * S : Target steering angle difference [target steering amount difference] θ' S : Converted steering angle [converted steering amount] θ' SO : Converted steering angle offset value [Converted steering amount offset value] γ: Steering gear ratio 1 / γ: Reverse gear ratio SCS: Status change signal Tq O : Operating torque (operating force) Tq C : Reaction torque [operation reaction force] Tq C-A : Assist component Tq C-L : Steering load dependent component Tq C-O : Operation angle deviation-dependent component [operation amount deviation-dependent component] Tq S : Steering torque (steering force) v: Vehicle speed (vehicle speed)

Claims

1. A steer-by-wire type steering system equipped in a vehicle, the system comprising: an operating member operated by a driver; a reaction force imparting device that imparts an operation reaction force to the operating member; a steering device that steers wheels; and a controller that controls the reaction force imparting device and the steering device, The controller: a steering control unit that determines a steering gear ratio from time to time and controls the steering device so that a ratio of an amount of steering of the wheels to an amount of operation of the operating member becomes the steering gear ratio; a converted operation amount determination unit that determines a converted operation amount by converting an actual steering amount of the wheels into an operation amount of the operation member based on the reciprocal of the determined steering gear ratio from moment to moment; a reaction force control unit that controls the reaction force application device based on an operation amount deviation, which is a difference between an actual operation amount of the operating member and the converted operation amount, so that the larger the operation amount deviation, the larger the operation reaction force becomes; having The converted manipulated variable determination unit When a steering state change signal indicating a sudden change in a steering gear ratio to be determined is input to the controller, a difference in the converted operation amount between immediately before and immediately after the time when the steering state change signal was input is converted into a difference in the steering amount of the wheels based on the steering gear ratio immediately after that time, and is grasped as a converted steering amount offset value, and from that time onwards, the converted steering amount offset value is gradually reduced and reconverted into a difference in the converted operation amount based on the reciprocal of the steering gear ratio which is determined each time, to determine a converted operation amount correction value, and the converted operation amount is corrected by the converted operation amount correction value.

2. The steering control unit, A target steering amount, which is a steering amount of the wheels to be realized, is determined from time to time based on an actual operation amount of the operating member and a steering gear ratio, and the steering device is controlled so that the actual steering amount of the wheels becomes the target steering amount; 2. The steering system according to claim 1, wherein, when the steering state change signal is input to the controller, a difference in the target steering amount between immediately before and immediately after the time when the steering state change signal is input is grasped as a target steering amount offset value, and from that time onwards, a target steering amount correction value is determined by gradually decreasing the target steering amount offset value, and the target steering amount is corrected by the target steering amount correction value.

3. The converted manipulated variable determination unit 3. The steering system according to claim 2, wherein the converted steering amount offset value is gradually decreased in accordance with a gradual decrease in the target steering amount offset value in the steering control section.

4. The steering control unit, 4. The steering system according to claim 1, further comprising a gear ratio determining section that determines a steering gear ratio based on an amount of operation of the operating member and a traveling speed of the vehicle.

5. the gear ratio determination unit is configured to determine the steering gear ratio to a specific steering gear ratio according to an operation amount of an operation member, regardless of the traveling speed of the vehicle, when the traveling speed of the vehicle cannot be recognized; 5. The steering system according to claim 4, wherein the steering state change signal is input to the controller when the traveling speed of the vehicle becomes unrecognizable.

6. The reaction force control unit is configured to determine an operation reaction force to be applied by combining a plurality of components, and to control the reaction force application device based on the determined operation reaction force, 6. A steering system according to claim 1, wherein the plurality of components include an assist component which is a component simulating a force for assisting the operation of the operating member by a driver in power steering, a steering load-dependent component based on a load of the steering device with respect to the steering of the wheels, and an operation amount deviation-dependent component based on the operation amount deviation.

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