Steering system

Abstract

To provide a highly practical vehicle behavior control system.SOLUTION: In a vehicle behavior control system, such as a steering system, an active stabilizer system, or an active suspension system for a vehicle, which includes an electric actuator 28 mounted on the vehicle and used for changing an attitude of the vehicle, a target value θ* of a control target of the electric actuator is determined based on at least one of an attitude δ to be taken by the vehicle and a factor for changing the attitude of the vehicle, a current IS is supplied to the electric actuator based on the target value, and current reduction processing for reducing a current supplied to the electric actuator is performed under a specific situation. As the current reduction processing, low-pass filter processing 404 performed on the target value, gain reduction processing and the like for reducing a proportional term gain KP and a differential term gain KD in PID feedback control can be adopted. Accordingly, the energy and power of the system can be saved.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a vehicle behavior control system for controlling the behavior of a vehicle. Specifically, the steering system of the steer-by-wire type Regarding. [Background technology]

[0002] In recent years, vehicles have come to use many systems that use electric actuators to control vehicle behavior, such as steer-by-wire steering systems, active stabilizer systems, and electromagnetic suspension systems. As vehicles become more and more electrified, there is a demand for energy saving in these vehicle behavior control systems. For example, in the steering system described in the following Patent Document, the power supply to the actuator is limited near the end of the steering range, i.e., near the steering end. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-218553 A Summary of the Invention [Problem to be solved by the invention]

[0004] The technology described in the above-mentioned patent documents is expected to be effective in terms of reducing the contact load on the stopper at the steering end, but it is difficult to say that it is necessarily sufficient in terms of energy saving. In other words, from the viewpoint of energy saving, there is still a lot of room for improvement in the vehicle behavior control system, and by implementing some kind of improvement, the practicality of the vehicle behavior control system will be improved. The present invention has been made in consideration of such a situation, and is a highly practical vehicle behavior control system. Steer-by-wire steering The objective is to provide a system. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention Foundational Vehicle Behavior Control System (Hereinafter, for convenience, this may be referred to as the "vehicle behavior control system of the present invention.") teeth, A vehicle behavior control system including an electric actuator mounted on a vehicle for changing the attitude of the vehicle, and a controller for controlling an amount of movement of the electric actuator or a force generated by the electric actuator as a control target, The controller: a target value of the controlled object is determined based on at least one of an attitude to be taken by the vehicle and a factor that changes the attitude of the vehicle, and a current is supplied to the electric actuator based on the target value; and A current reduction process is configured to reduce the current supplied to the electric actuator under a specific situation. 、 The steering system of the present invention specifically includes: A steer-by-wire steering system comprising: a steering operation member operated by a driver; a reaction motor which applies an operation reaction force to the operation of the steering operation member; a steering device having an electric actuator for steering wheels; and a controller for causing the steering device to steer the wheels by controlling an amount of steering of the wheels corresponding to an amount of operation of the electric actuator, the steering system being configured to steer the wheels by a force generated by the electric actuator without relying on a steering operation force of a driver and mounted on a vehicle, The vehicle is capable of both manual and automated driving, The controller: A target steering amount, which is a target for the steering amount of the wheels, is determined based on the operation amount of the steering operation member during manual driving, and is obtained based on information from an automatic driving electronic control unit during automatic driving, and a current is supplied to the electric actuator based on the target steering amount; and The current reduction process for reducing the current supplied to the electric actuator is configured to be performed when the vehicle's traveling speed is equal to or lower than a set traveling speed during manual driving, and to be performed regardless of the vehicle's traveling speed during automatic driving. Effect of the Invention

[0006] In the vehicle behavior control system of the present invention, the current supply to the electric actuator is reduced in a specific situation by the current reduction process compared to when the specific situation is not present, so that a relatively large energy saving effect can be expected. As a result, the vehicle behavior control system of the present invention has high practicality.

[0007] The vehicle behavior control system of the present invention is not particularly limited in terms of its specific structure, function, use, etc., as long as it includes an electric actuator (hereinafter sometimes simply referred to as "actuator") for changing the attitude of the vehicle, and a controller for controlling the amount of movement of the actuator or the force generated by the actuator (hereinafter sometimes referred to as "actuator force") as the control object. The actuator may be one that uses an electric motor as a drive source, for example. The "attitude of the vehicle" changed by the actuator refers to the pitch attitude, roll attitude (inclination of the vehicle body in the longitudinal direction and width direction), slip angle with respect to the traveling direction of the vehicle (turning direction and degree of turning), etc.

[0008] Specifically, the present invention can be applied to a steering system that steers wheels, an active stabilizer system that is equipped with a stabilizer bar to suppress roll of the vehicle body and can control the roll suppression force exerted by the stabilizer bar, and an active suspension system that applies bound and rebound forces to the vehicle body and wheels and can control these forces.

[0009] More specifically, when the vehicle behavior control system of the present invention is a steering system, the steering system may be a system that assists the driver's steering force with a force generated by an electric actuator, that is, a so-called power steering system, or a system that steers the wheels with a force generated by an actuator without relying on the driver's steering force, that is, a so-called steer-by-wire steering system (hereinafter, sometimes referred to as a "steer-by-wire system"). In the case of a steer-by-wire system, since the actuator operation amount and the wheel steering amount generally have a specific relationship, the actuator operation amount may be the control target of the controller. Then, the controller grasps the operation amount of a steering member such as a steering wheel as an index of the attitude that the vehicle should take, and determines the wheel steering amount, that is, a target value of the actuator operation amount, based on the operation amount, and supplies a current to the actuator based on the target value.

[0010] When the vehicle behavior control system of the present invention is an active stabilizer system, the actuator is for changing the roll attitude of the vehicle body. Specifically, when the vehicle is provided with a stabilizer bar whose both ends are connected to the left and right wheels, respectively, for suppressing the roll of the vehicle body, the actuator may be configured to change the roll suppression force exerted by the stabilizer bar. In this case, the control target of the controller may be the actuator operation amount when the roll suppression force exerted by the stabilizer bar depends on the actuator operation amount, or the actuator force when the roll suppression force depends on the actuator force. The controller may grasp the lateral acceleration occurring in the vehicle body, the yaw rate of the vehicle body and the vehicle travel speed (hereinafter sometimes referred to as "vehicle speed"), the lateral force acting on the vehicle body, and the like, as factors that change the attitude of the vehicle, and may determine a target value of the actuator operation amount or actuator force based on the lateral acceleration, and may supply a current to the actuator based on the target value.

[0011] When the vehicle behavior control system of the present invention is an active suspension system, the actuator is for changing the pitch attitude, roll attitude, bounce attitude, etc. of the vehicle body, in other words, the relative distance in the vertical direction between each wheel and the vehicle body (hereinafter, sometimes referred to as "stroke amount"). When the actuator force is configured to directly act between the wheel and the vehicle body, the actuator force may be the control target of the controller. The actuator force may be made to act as a damping force for the relative movement between the vehicle body and the wheel, or may be made to act as a force for directly changing the stroke amount (hereinafter, sometimes referred to as "stroke amount changing force"). Furthermore, the actuator force may be made to act as a force obtained by combining a component of the damping force and a component of the stroke amount changing force. For example, when the actuator is for changing the pitch attitude and roll attitude of the vehicle body, the actuator force, more specifically, the stroke amount changing component of the actuator force, may be made the control target of the controller. The controller then grasps the longitudinal acceleration and lateral acceleration acting on the vehicle body as factors that change the vehicle posture, and determines a target value for the actuator force, or more specifically, the stroke amount modification component of the actuator force, based on the longitudinal acceleration and lateral acceleration, and supplies current to the actuator based on that target value.

[0012] In the vehicle behavior control system of the present invention, the current reduction process is performed under a specific situation. Considering that the vehicle behavior control system is a system for controlling the behavior of a vehicle, it is expected that the responsiveness of the system regarding the control, that is, the responsiveness of the actuator operation, will decrease by reducing the current supplied to the actuator. In other words, it is expected that it will take some time for the actuator operation amount and actuator force to reach the planned operation amount and force. Therefore, it is desirable to perform the current reduction process under a specific situation in which the actuator is not required to be responsive. Specifically, for example, in consideration of the fact that the system is generally not required to be responsive when the vehicle speed is low, the current reduction process may be performed when the vehicle speed is below a set speed, which is considered to be the specific situation. In addition, for example, in the case where the vehicle is capable of running both manually and automatically by the driver, in consideration of the fact that the vehicle is generally not required to be operated in a responsive manner during automatic driving, which is to say, to be operated somewhat radically, the current reduction process may be performed when the vehicle is running in automatic driving, which is considered to be the specific situation, which is considered to be.

[0013] The method to be followed when performing the current reduction process is not particularly limited, but for example, the controller may perform the current reduction process according to the method specifically described below.

[0014] As described above, the controller determines the target value of the controlled object. To perform the current reduction process according to one method, the controller can be configured to apply low-pass filtering to the target value only under a specific situation, or to lower the cutoff frequency of the low-pass filtering process applied to the target value under a specific situation compared to when the specific situation is not present. The low-pass filter causes a delay in the output of the target value, and the low-pass filter can suppress a sudden change in the target value. Furthermore, by lowering the cutoff frequency of the low-pass filter, the change rate of the target value can be further slowed down. By using such a method, it is possible to reduce the current supplied to the actuator.

[0015] The controller can be configured to supply current to the actuator by feedback control based on the deviation of the actual value from the target value of the controlled object. In such a configuration, in order to perform a current reduction process according to another method, the controller can also be configured to reduce the gain in the feedback control in a specific situation compared to when the specific situation is not present. By such a method, it becomes possible to reduce the current supplied to the actuator. Incidentally, the feedback control can be performed by adding together a proportional term component, a differential term component, and an integral term component, as will be described in detail later. In that case, only the gain for determining the proportional term component and the differential term component, which are components that contribute to responsiveness, may be reduced in the current reduction process.

[0016] In the current reduction process, either one of the above two techniques may be adopted, or both may be adopted. [Brief description of the drawings]

[0017] [Figure 1] 1 is a diagram showing an overall configuration of a vehicle steering system which is a vehicle behavior control system according to a first embodiment. [Diagram 2]1 is an overall view of a steering actuator constituting a steering system for a vehicle, and a cross-sectional view of a portion in which a steering amount sensor is disposed. [Diagram 3] FIG. 4 is a cross-sectional view of the steering actuator for illustrating a steering motor and a motion converting mechanism. [Figure 4] 11 is a graph showing map data for determining or setting, based on vehicle speed, a steering gear ratio, a cutoff frequency in low-pass filter processing, and a proportional term gain and a differential term gain used to determine a steering current. [Diagram 5] FIG. 2 is a block diagram showing the functions of a steering electronic control unit. [Figure 6] 11 is a graph for explaining the effect of low-pass filtering applied to a target steering amount. [Figure 7] 4 is a flowchart of a steering control program executed in a steering electronic control unit. [Figure 8] FIG. 1 is a diagram showing an overall configuration of an active stabilizer system which is a vehicle behavior control system according to a second embodiment. [Figure 9] FIG. 2 is a diagram showing front and rear wheel stabilizer devices constituting the active stabilizer system. [Figure 10] 4 is a cross-sectional view of an actuator included in the stabilizer device. FIG. [Figure 11] 4 is a flowchart of a stabilizer control program executed in a stabilizer electronic control unit. [Figure 12] FIG. 11 is a diagram showing the overall configuration of an active suspension system which is a vehicle behavior control system according to a third embodiment. [Figure 13] FIG. 1 is a diagram showing a suspension device that constitutes an active suspension system. [Figure 14] FIG. 2 is a cross-sectional view showing an electromagnetic actuator of the suspension device. [Figure 15] FIG. 2 is a cross-sectional view showing a damper of a suspension device. [Figure 16]1 is a conceptual diagram showing an actual device model and a control model of a suspension device. [Figure 17] 4 is a flowchart of a suspension control program executed in a suspension electronic control unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, as a mode for carrying out the present invention, a vehicle steering system, an active stabilizer system, and an active suspension system, which are embodiments of the present invention, will be described in detail with reference to the drawings. In addition to the following embodiments, the present invention can be carried out in various forms including those described in the above section "Modes of the Invention" and various modifications and improvements based on the knowledge of those skilled in the art. EXAMPLES

[0019] [1] Vehicle steering system (first embodiment) A vehicle steering system (hereinafter, sometimes simply referred to as a "steering system") which is a vehicle behavior control system according to a first embodiment will be described below.

[0020] (a) Configuration of a vehicle steering system i) Overall structure As shown diagrammatically in FIG. 1, this steering system is a steer-by-wire type steering system that steers two wheels 12, one on the left and one on the right, which are the front wheels of a vehicle 10, and is broadly composed of a steering device 14 for steering the wheels 12, an operation device 18 having a steering wheel 16 which is a steering operation member operated by the driver, and a steering electronic control unit 20 (hereinafter sometimes referred to as "steering ECU 20") which serves as a controller for causing the steering device 14 to steer the wheels 12 in accordance with the operation of the steering wheel 16.

[0021] Each of the wheels 12 is rotatably held by a steering knuckle (not shown) that is rotatably supported on the vehicle body via a suspension device. The steering device 14 is configured to include a steering actuator 28, which is an electric actuator having a steering motor 24, which is an electric motor as a drive source, and which moves a steering rod 26 left and right, and link rods 32, one end of which is connected via a ball joint 30 to both ends of the steering rod 26. The other end of each of the link rods 32 is connected via a ball joint (not shown) to a knuckle arm (not shown) provided on the corresponding steering knuckle. When the steering rod 26 is moved left and right, each steering knuckle rotates and each of the wheels 12 is steered.

[0022] ii) Structure of steering actuator The steering actuator 28 constituting the steering device 14 is mounted on the vehicle 10 to change the attitude of the vehicle 10, more specifically, to change the orientation (direction) of the vehicle 10 with respect to the traveling direction, that is, the slip angle of the vehicle 10. The basic structure of the steering actuator 28 will be described with reference to Figs. 2 and 3. As can be seen from Fig. 2(a) showing the overall appearance of the steering actuator 28 and Fig. 3 showing the inside of the steering motor 24 and the inside of the steering actuator 28, the steering rod 26 is held in the housing 40 so as to be unable to rotate around its axis and to be movable left and right. A screw groove 42 is formed on the outer periphery of the steering rod 26. Also, a retaining tube 44 is held in the housing 40 so as to be able to rotate around its axis and to be unable to move left and right. A nut 46 that holds a bearing ball is fixedly held in the retaining tube 44. The nut 46 and the steering rod 26 are screwed together to form a ball screw mechanism. In other words, it can be considered that a screw mechanism is configured including a screw provided on the steering rod 26 and a nut 46 provided with a screw that screws into the screw.

[0023] The steering motor 24 is disposed outside the housing 40 with its own axis and the axis of the steering rod 26 parallel to each other, and a timing pulley 50 is attached to one end of a motor rotating shaft 48 (hereinafter sometimes simply referred to as "motor shaft 48"). Engagement teeth 52 are formed on the outer periphery of the retaining cylinder 44, similar to the timing pulley 50, and the retaining cylinder 44 functions as another timing pulley that forms a pair with the timing pulley 50. A timing belt 54 serving as a transmission belt is wound around the retaining cylinder 44 and the timing pulley 50, and the rotation of the steering motor 24 (strictly speaking, the rotation of the motor shaft 48) rotates the nut 46, and the steering rod 26 is moved in the left-right direction in a direction that corresponds to the rotation direction of the steering motor 24. In other words, a belt transmission mechanism is provided that includes the retaining tube 44, timing pulley 50, and timing belt 54, and this belt transmission mechanism and the above-mentioned screw mechanism provide a motion conversion mechanism 55 that converts the rotational motion of the motor shaft 48 into motion of the steering rod 26 with an amount of motion corresponding to the amount of rotational motion.

[0024] In this steering system, steering motor 24 is a three-phase brushless DC motor. More specifically, magnets 56 are fixedly arranged in a line in the circumferential direction on the outer periphery of motor shaft 48, and coil 58 is arranged facing magnets 56 and held in motor housing 59, which is the housing of steering motor 24. Steering motor 24 rotates when current is applied to coil 58. The torque generated by steering motor 24, i.e., the force that moves steering rod 26 left and right, is generally proportional to the current supplied to coil 58.

[0025] iii) Configuration of the operation device As shown in FIG. 1, the operating device 18 includes the steering wheel 16, a steering shaft 60 fixed to the steering wheel 16 so as to be rotatable integrally with the steering wheel 16, and a reaction motor 62 which is an electric motor. The motor shaft of the reaction motor 62 is integral with the steering shaft 60, and the reaction motor 62 applies a rotational torque to the steering wheel 16. This rotational torque functions as a reaction force (operation reaction force) against the operation of the steering wheel 16 by the driver, that is, against the steering operation. Therefore, the reaction motor 62 constitutes a reaction actuator. Although a detailed structure of the reaction motor 62 is not shown, the reaction motor 62 is a brushless DC motor like the turning motor 24. The operation reaction force is generated by energizing the reaction motor 62, and the magnitude of the operation reaction force is generally proportional to the current supplied to the reaction motor 62. The operation reaction force also functions as a force that returns the steering wheel 16 to a neutral position (a position where the steering wheel is not operated to the right or left).

[0026] iv) Control configuration The steering ECU 20, which is responsible for controlling the steering system, is configured to include a computer constituted by a CPU, ROM, RAM, etc., and inverters which are drive circuits (drivers) for each of the steering motor 24 and the reaction motor 62. As can be seen from Fig. 1, in detail, each inverter of the steering ECU 20 is connected to a battery 66 which is a power source via a converter 64, and supplies current to each of the steering motor 24 and the reaction motor 62 based on commands from the computer.

[0027] Various sensors are provided in the steering device 14 and the operating device 18 to detect their operating states. The steering ECU 20 performs control based on the detection values ​​of these sensors. Specifically, the steering actuator 28 is provided with a steering amount sensor 80 for detecting the amount of movement of the steering rod 26, i.e., the left-right operating position of the steering rod 26, as the steering amount (steered angle) θ of the wheels 12. To explain this in detail with reference to FIG. 2(b), which shows a cross section of a portion of the steering actuator 28 where the steering amount sensor 80 is provided, a rack 82 is formed on the steering rod 26, and a pinion shaft 86 having a pinion 84 meshing with the rack 82 is held in the housing 40. Incidentally, the steering actuator 28 is an actuator used in a so-called power steering system, and the pinion shaft 86 is connected to an input shaft 90 via a torsion bar 88. In this steering system, in place of a torque sensor for detecting steering torque when the steering actuator 28 is employed in a power steering system, a steering amount sensor 80 is provided. Meanwhile, the steering device 18 is provided with an operation amount sensor 92 for detecting the operation amount (operation angle) δ of the steering wheel 16. The steering amount sensor 80 and the operation amount sensor 92 are so-called steering sensors and have a general structure, so a detailed description thereof will be omitted here.

[0028] Each wheel 12 has its own rotation speed, i.e., wheel speed v W The steering ECU 20 is configured to estimate a vehicle speed v, which is the traveling speed of the vehicle 10, based on the detection values ​​of the wheel speed sensors 94.

[0029] The vehicle 10 is capable of automatic driving, and the instrument panel is provided with an automatic driving switch 96 for executing automatic driving, and further with a driving mode selection switch 98 for switching the driving mode. Although a detailed explanation is omitted, the driving modes are an ECO mode that prioritizes fuel efficiency, and a sports mode for realizing brisk driving, and the mode selection switch 98 is adapted to switch between these two modes. The automatic driving switch 96 and the mode selection switch 98 are also connected to the steering ECU 20.

[0030] (b) Control of a steering system for a vehicle In this steering system, the steering ECU 20, which is the controller, more specifically, the computer of the steering ECU 20, controls the steering of the wheels 12 with the steering actuator 28 (hereinafter, sometimes referred to as "steering control") in order to control the slip angle of the vehicle 10. Also, in order to apply an operation reaction force against the steering operation by the driver to the steering wheel 16, the steering ECU 20 executes reaction force control with respect to the operation device 18, more specifically, reaction force motor 62 of the operation device 18. Since this reaction force control is a general control, a description of the reaction force control will be omitted here, and the steering control will be described in detail below.

[0031] i) Basic steering control Simply put, the steering control is a control for realizing the steering of the wheels 12 in response to a steering request. When the vehicle 10 is being manually driven, the operation amount δ of the steering wheel 16 detected by the operation amount sensor 92 is the steering request, and the steering ECU 20 determines a target steering amount θ, which is a target for the steering amount θ of the wheels 12, based on the operation amount δ. * In more detail, the steering system employs a variable gear ratio system (VGRS), and the steering ECU 20 determines the wheel speed v detected by the wheel speed sensor 94. WBased on this, the vehicle speed v of the vehicle 10 is estimated, and a steering gear ratio (ratio of steering amount θ to operation amount δ) γ corresponding to the vehicle speed v is determined. The steering gear ratio γ is determined by referring to map data stored in the steering ECU 20. Although a detailed explanation is omitted, the steering gear ratio γ is set to be smaller as the vehicle speed v increases, as shown in FIG. 4(a). Then, the steering ECU 20 calculates, according to the following equation, θ * = γ δ Target steering amount θ * Determine.

[0032] On the other hand, when the vehicle 10 is being driven automatically by operation of the automatic driving switch 96, the steering ECU 20 determines the target steering amount θ based on information transmitted from an automatic driving electronic control unit (hereinafter, sometimes referred to as an "automatic driving ECU"; not shown). * Obtain.

[0033] The steering amount θ can be considered as the amount of movement of the steering rod 26 in the left-right direction, i.e., the amount of operation of the steering actuator 28, and is the subject of control in the steering control of the steering system. * is a target value for the control object. Incidentally, in this steering system, it is defined as the rotation amount (rotation position) of pinion shaft 86 of steering actuator 28.

[0034] The steering ECU 20 detects an actual steering amount θ (hereinafter, sometimes referred to as an "actual steering amount θ") via a steering amount sensor 80 provided in the steering actuator 28 as an actual value of the controlled object. * A steering amount deviation Δθ, which is the deviation of the actual steering amount θ from the steering amount θ, is determined, and a current (hereinafter sometimes referred to as "steering current") I to be supplied to the steering motor 24 is determined according to a feedback control technique based on the steering amount deviation Δθ. S In detail, the steering current I is determined according to the following formula: S Determine. IS =K P Δθ+K D dΔθ / dt+K I ∫Δθdt The first, second, and third terms on the right side of the above equation are the proportional, differential, and integral components, respectively, and K P ,K D ,K I are the proportional gain, the differential gain, and the integral gain, respectively. The steering ECU 20 controls the steering current I S Based on this, a current is supplied to the steering motor 24 via an inverter.

[0035] ii) Current reduction processing In the present steering system, in consideration of energy saving and electricity saving, under specific circumstances, a current reduction process is performed on the current supplied to the steering actuator 28. The contents of this current reduction process will be described below.

[0036] If the current supplied to steering actuator 28 is reduced, the force generated by steering actuator 28 (hereinafter sometimes referred to as "actuator force") will decrease, and there is a possibility that a delay will occur in the operation of steering actuator 28. In other words, the responsiveness of steering actuator 28 will decrease. Specifically, in steering of wheels 12, the change in actual steering amount θ will be greater than the change in target steering amount θ * This may cause a situation where the steering angle does not follow the change in the target steering amount θ * is large, in other words, when a relatively sudden steering operation is performed or when a relatively large actuator force is required.

[0037] Therefore, in this steering system, the specific situation in which the current reduction process is performed is limited to a situation in which the responsiveness of the operation of the electric actuator is not required. Specifically, for example, when the vehicle speed v is high, the self-aligning torque acting on the steered wheels 12 becomes large, and a relatively large actuator force is required, and a certain degree of high responsiveness is required from the viewpoint of the operation feeling, operation stability, etc. of the vehicle 10. In view of these, when the vehicle speed v is low, more specifically, when the vehicle speed v is below the threshold vehicle speed v TH When the speed is lower than the predetermined speed (for example, 20 to 30 km / h), the steering ECU 20 determines that the situation is a specific one, and performs a current reduction process.

[0038] In this steering system, two current reduction processes with different methods are executed. One of the two current reduction processes reduces the target steering amount θ * In more detail, the steering ECU 20 performs low-pass filtering on the target steering amount θ * , the cutoff frequency f C A target steering amount θ having a higher frequency * In other words, the cutoff frequency f C A target steering amount θ having a higher frequency * The process of creating a delay is performed for the change in the cutoff frequency f C As shown in the graph of FIG. 4(b), when the vehicle speed v is greater than the threshold vehicle speed v TH When the low frequency f CL The vehicle 10 has two driving modes, one of which is an ECO mode that emphasizes energy saving, and the other is a sports mode that emphasizes vehicle dynamics. The graph shows the cutoff frequency f C The changes in f are shown by solid and dashed lines, respectively. As can be seen from the graphs, taking into account the difference in the degree of response required, CL , and in ECO mode, the low frequency f CL1However, in the case of sports mode, the low frequency f CL2 (f CL1 ) is set. The cutoff frequency f C As can be seen from the graph, in any driving mode, the vehicle speed v is equal to or greater than the threshold vehicle speed v TH As the vehicle speed exceeds a certain level, the frequency f CH For example, the low frequency f CL1 is about 5Hz, low frequency f CL2 is about 10Hz, high frequency f CH can be about 30 Hz.

[0039] The other of the two current reduction processes is the reduction of the steering current I S In determining the proportional gain K P , Differential term gain K D Specifically, as shown in the graph of FIG. 4(c), when the vehicle speed v is greater than or equal to the threshold vehicle speed v TH When the following occurs, the proportional gain K related to the responsiveness P , Differential term gain K D However, low gain K PL ,Low Gain K DL Then, the vehicle speed v is set to the threshold vehicle speed v TH As the vehicle speed v increases beyond a certain level, the gain is set to gradually increase. PH ,High Gain K DH is set to.

[0040] As described above, the vehicle 10 can be driven both manually and automatically, and is set so that the vehicle 10 is steered only slowly during automatic driving. In consideration of this, the steering ECU 20 is configured to perform a current reduction process when the vehicle is automatically driven, regardless of the vehicle speed v, assuming that the vehicle is in a specific situation.

[0041] In detail, in the case of manual operation, the cutoff frequency f C , steering current I S The proportional gain K in determining P , Differential term gain K D As described above, the cutoff frequency f is set depending on the vehicle speed v. However, in the case of autonomous driving, the cutoff frequency f is set regardless of the vehicle speed v. C But at low frequencies f CL1 , the proportional gain K P , Differential term gain K D But low gain K PL ,Low Gain K DL are set to, respectively.

[0042] In this steering system, the target steering amount θ * However, when the specific situation is not present, the filtering process may not be performed. In addition, in this steering system, the filtering process, the proportional term gain K P , Differential term gain K D In the setting, the vehicle speed v is the threshold vehicle speed v TH When the vehicle speed exceeds the threshold, the cut-off frequency f C , proportional term gain K P , Differential term gain K D , respectively, for low frequency f CL , low gain K PL ,Low Gain K DL to high frequency f CH , high gain K PH ,High Gain K DH The threshold value v is set to 0.5 V. TH When the cutoff frequency f C , proportional term gain K P , Differential term gain K D , respectively, for stepwise high frequencies f CH , high gain K PH ,High Gain K DH Furthermore, in the present steering system, the cutoff frequency f C and the change in steering current IS The proportional gain K in determining P , Differential term gain K D In the above embodiment, both the above-mentioned changes are performed, but it is also possible to perform only one of them.

[0043] iii) Functional block diagram for steering control The function of the steering ECU 20 regarding the steering control including the current reduction process described above is shown in a block diagram in FIG. 5. The steering ECU 20 detects the wheel speed v of each of the four wheels 12 by the wheel speed sensor 94. W Based on the vehicle speed v, a vehicle speed estimating unit 400 is provided which estimates the vehicle speed v of the vehicle 10 based on the vehicle speed v, and based on map data as shown in FIG. 4(a), a steering gear ratio γ is determined, and based on the steering gear ratio γ and the operation amount δ of the steering wheel 16 detected by the operation amount sensor 92, a target steering amount θ is determined. * The target steering amount determining unit 402 determines the target steering amount.

[0044] Then, the steering ECU 20 calculates the target turning amount θ * The low-pass filter 404 has a general configuration, and in simple terms, includes an integral element 406 and a proportional element 408. "a" in the proportional element 408 is defined by the following equation. a=1 / TT: time constant Moreover, the transfer function G(s) of the low-pass filter 404 is expressed by the following equation. G(s)=1 / (1+T s) s: Laplace operator Furthermore, the time constant T and the cutoff frequency f C The relationship between them can be expressed by the following equation: T=1 / (2 π f C )

[0045] As described above, the low-pass filter 404 determines the cutoff frequency f based on the estimated vehicle speed v by referring to map data such as that shown in FIG. 4(b) when the vehicle 10 is being manually driven. C and when the vehicle 10 is autonomously driven, the cut-off frequency f C The low frequency f CL1 Then, the cutoff frequency f C Based on this, the time constant T is determined and filtering is performed.

[0046] The steering ECU 20 outputs the filtered target steering amount θ * The steering ECU 20 determines a steering amount deviation Δθ, which is the deviation of the actual steering amount θ detected by the steering amount sensor 80 of the actuator 28 with respect to the steering amount deviation Δθ. The steering ECU 20 has a proportional term gain multiplier 410, a differential term gain multiplier 412, an integral term gain multiplier 414, a differentiator 416, and an integrator 418, and calculates a steering current I S The proportional component of the steering current I S The differential component of the steering current I S Then, the steering ECU 20 adds up these components to obtain the steering current I S In determining the proportional component and the differential component, the steering ECU 20 determines whether the vehicle 10 is being driven automatically or manually. When the vehicle 10 is being driven manually, the steering ECU 20 determines the proportional term gain K P , Differential term gain K D When the vehicle 10 is being driven autonomously, the proportional term gain K P , Differential term gain K D , low gain K PL ,Low Gain K DL The determined steering current I SThe command for is sent to the inverter 420, which supplies the current to the steering motor 24 of the actuator 28.

[0047] iv) Effect of current reduction processing Next, the effect of the current reduction process, specifically, the target turning amount θ * The effect of low-pass filtering on the target steering amount θ with respect to the time t when no filtering is applied will be described with reference to Fig. 6. The graphs in Fig. 6(a) and Fig. 6(b) show the relationship between the target steering amount θ * ,Change in actual steering amount θ, steering current I S The graphs in FIG. 6(c) and FIG. 6(d) show the change in the target steering amount θ with respect to the passage of time t when filtering is applied. * ,Change in actual steering amount θ, steering current I S The changes in the cutoff frequency f C is set to 5 Hz, and the steering conditions, i.e., the vehicle speed v, the operation amount δ of the steering wheel 16, the operation speed dδ / dt, etc., are the same whether the filtering is applied or not. Incidentally, the operation of the steering wheel 16 is performed at time t 0 The steering motor 24 is a three-phase brushless motor, and the steering current I S The currents of the U phase, V phase, and W phase are shown.

[0048] As can be seen from the graph of FIG. 6(a), when filtering is not performed, the target steering amount θ * The increase gradient of is relatively steep, and the actual steering amount θ is smaller than the target steering amount θ * On the other hand, as can be seen from the graph in FIG. 6(c), when filtering is applied, the target steering amount θ * The increase gradient of is relatively gentle, and the actual steering amount θ is greater than the target steering amount θ *As a result, as can be seen by comparing the graphs in Fig. 6(b) and (d), the amplitude of the current in each phase is smaller when filtering is applied than when filtering is not applied. In other words, the steering current I S is reduced by applying the filter process.

[0049] v) Control Flow The steering control described above is performed by the computer of the steering ECU 20 repeatedly executing the steering control program shown in the flowchart of Fig. 7 at short intervals (for example, several meters to several tens of milliseconds). Below, the flow of processing according to the steering control program will be briefly described with reference to the flowchart.

[0050] In processing according to the steering control program, first, in step 1 (hereinafter abbreviated as "S1", the same applies to the other steps), it is determined whether or not the vehicle 10 is being driven automatically based on the operation state of the automatic driving switch 96. If the vehicle is not being driven automatically, that is, if it is being driven manually, then in S2 the automatic driving flag FLAD is set to "0". The automatic driving flag FLAD is a flag that is set to "0" when the vehicle is being driven manually and is set to "1" when the vehicle is being driven automatically.

[0051] In the next step S3, the wheel speed v of each wheel 12 detected by the wheel speed sensor 94 is W In step S4, the vehicle speed v of the vehicle 10 is estimated based on the estimated vehicle speed v, and the steering gear ratio γ is determined by referring to the map data shown in FIG. 4(a) based on the estimated vehicle speed v. In step S5, the target steering amount θ is calculated based on the estimated vehicle speed v and the map data shown in FIG. * is determined.

[0052] If it is determined in S1 that the vehicle is being driven automatically, in S6, the automatic driving flag FLAD is set to "1", and in S7, the target steering amount θ is set based on the information transmitted from the automatic driving ECU. *is obtained.

[0053] In the next step S8, a determination is made based on the flag value of the automatic driving flag FLAD. If the vehicle is being driven manually, in step S9, the currently selected driving mode, i.e., whether it is the ECO mode or the sports mode, is identified based on the operation state of the driving mode selection switch 98. Then, based on the identified current driving mode and vehicle speed v, map data such as that shown in FIG. 4(b) is referenced to determine the cutoff frequency f in the filtering process. C On the other hand, when the vehicle is in automatic operation, the cutoff frequency f C is the low frequency f CL1 Then, in S12, the determined target steering amount θ * The low-pass filter process described above is performed on the signal. The specific process of the low-pass filter process executed in the program is a common one, and therefore will not be described here.

[0054] In the next step S13, a determination is made again based on the flag value of the automatic driving flag FLAD. If the vehicle is being manually driven, in step S14, the steering current I S The proportional gain K used in determining P , Differential term gain K D On the other hand, when the vehicle is in automatic driving mode, the proportional gain K P , Differential term gain K D However, low gain K PL ,Low Gain K DL is set to.

[0055] In the next step S16, the actual steering amount θ is detected by the steering amount sensor 80, and in step S17, the filtered target steering amount θ * The steering amount deviation Δθ, which is the deviation of the actual steering amount θ from the P , Differential term gain KD , integral term gain K I Based on this, the steering current I to be supplied to the steering motor 24 is calculated by the above method according to the PID feedback control law. S Then, in S18, the steering current I S is supplied, and one execution of the steering control program is completed.

[0056] [2] Active stabilizer system (second embodiment) An active stabilizer system (hereinafter, may be simply referred to as a "stabilizer system"), which is a vehicle behavior control system according to the second embodiment, will be described below. This stabilizer system is mounted on a vehicle 10 in which the above-mentioned steering system is mounted.

[0057] (a) Active stabilizer system configuration As shown in Fig. 8, this stabilizer system includes two stabilizer devices 114 disposed on the front and rear wheel sides of the vehicle 10. Each of the stabilizer devices 114 includes a stabilizer bar 120 connected to a suspension lower arm (not shown) as a wheel holding member that holds the left and right wheels 12 at both ends via a link rod 118 as a connecting member (see Fig. 9). The stabilizer bar 120 includes a pair of stabilizer bar members that are split from the stabilizer bar 120, i.e., a right stabilizer bar member 122 and a left stabilizer bar member 124. The pair of stabilizer bar members 122, 124 are connected to each other via an actuator 130, which is an electric actuator, so as to be capable of relative rotation, and roughly speaking, the stabilizer device 114 changes the apparent rigidity of the entire stabilizer bar 120 (hereinafter, sometimes referred to as "stabilizer rigidity") to suppress roll of the vehicle body by the actuator 130 rotating the left and right stabilizer bar members 122, 124 relative to each other. Note that, since the stabilizer system has partially different configurations between the front wheel side stabilizer device 114 and the rear wheel side stabilizer device 114, in the following description, when it is necessary to distinguish between the front wheel side and the rear wheel side, the front wheel side is given an f and the rear wheel side is given an r, and when it is necessary to further distinguish between the left and right sides, the respective symbols are given an fr, a fl, a rr, and a rl (meaning the right front wheel side, the left front wheel side, the right rear wheel side, and the left rear wheel side, respectively).

[0058] As shown in Fig. 9(a), each of the stabilizer bar members 122f, 124f of the front wheel side stabilizer device 114f can be divided into a torsion bar portion 160fr, 160fl extending generally in the vehicle width direction, and an arm portion 162 integrated with each of the torsion bar portions 160fr, 160fl and extending generally toward the rear of the vehicle, intersecting the torsion bar portion 160fr, 160fl. The torsion bar portion 160fr of the right stabilizer bar member 122f is formed relatively short, and the torsion bar portion 160fl of the left stabilizer bar member 124f is formed relatively long. The left stabilizer bar member 124f is further shaped to have a shift portion 163 which is a bent portion when the torsion bar portion 160fl is shifted from the axis. On the other hand, in the rear-wheel stabilizer device 114r, as shown in Fig. 9(b), the pair of stabilizer bar members 122r, 124r can be divided into torsion bar portions 160rr, 160rl extending to approximately the same length in the vehicle width direction, and an arm portion 162 integrated with each of the torsion bar portions 160rr, 160rl and intersecting therewith, extending generally forward of the vehicle. Unlike the front-wheel stabilizer device 114f, both of the torsion bar portions 160rr, 160rl have a linear shape, and the lengths between the actuator 130 and the arm portion 162 are approximately equal to each other.

[0059] The torsion bar portions 160 of the stabilizer bar members 122f, 122r, 124f, and 124r are rotatably supported by a support portion 164 fixedly provided on the vehicle body at a location close to the arm portion 162, and are arranged coaxially with each other. In both the front-wheel side stabilizer device 114f and the rear-wheel side stabilizer device 114r, the actuator 130 described above is arranged so as to connect the left and right torsion bar portions 160, and as will be described in detail later, the ends of the torsion bar portions 160 (the ends opposite the arm portion 162) are connected to the actuators 130. From the above-mentioned configuration, the front-wheel side stabilizer device 114f is structured such that the actuator 130 is arranged at a position shifted from the center to the right in the vehicle width direction, and the rear-wheel side stabilizer device 114r is structured such that the actuator 130 is arranged at approximately the center in the vehicle width direction. On the other hand, an end of each arm portion 162 (an end opposite to the torsion bar portion 160 side) is connected to a wheel holding member via a link rod 118. In the front-wheel stabilizer device 114f, a regulating member 166 fixedly provided to the torsion bar portion 160fl and the actuator 130 are adapted to abut against opposing side surfaces of the two support portions 164, thereby regulating positional fluctuation in the vehicle width direction, and in the rear-wheel stabilizer device 114r, a regulating member 166 fixedly provided to each of the torsion bar portions 160rr, 160rl are adapted to abut against opposing side surfaces of the two support portions 164, thereby regulating positional fluctuation in the vehicle width direction.

[0060] The actuator 130 has the same structure for both the front-wheel side and rear-wheel side stabilizer devices 114, and includes an electric motor 170 as a drive source and a reducer 172 for reducing the rotation of the electric motor 170, as shown in FIG. 10. The electric motor 170 and the reducer 172 are provided in a housing 174 which is an outer shell member of the actuator 130. As can be seen from the figure, the left stabilizer bar member 124 is fixedly connected to an end of the housing 174, and the right stabilizer bar member 122 is disposed so as to extend into the housing 174, and is supported so as to be rotatable relative to the housing 174 but not movable in the axial direction. The end of the right stabilizer bar member 122 present in the housing 174 is connected to the reducer 172.

[0061] The electric motor 170 includes a plurality of stator coils 184 fixedly arranged on one circumference along the inner surface of the peripheral wall of the housing 174, a hollow motor shaft 186 rotatably held in the housing 174, and a permanent magnet 188 fixedly arranged on one circumference on the outer periphery of the motor shaft 186 so as to face the stator coils 184. The electric motor 170 is a three-phase DC brushless motor in which the stator coils 184 function as a stator and the permanent magnets 188 function as a rotor.

[0062] The reduction gear 172 includes a wave generator 190, a flexible gear (flexspline) 192, and a ring gear (circular spline) 194, and is configured to include a harmonic gear mechanism. The wave generator 190 includes an elliptical cam and a ball bearing fitted on its outer periphery, and is fixed to one end of the motor shaft 186. The flexible gear 192 has a cup-shaped peripheral wall that is elastically deformable, and a plurality of teeth are formed on the outer periphery of the opening side of the peripheral wall. This flexible gear 192 is connected to the right stabilizer bar member 122 described above and is supported thereby. In more detail, the right stabilizer bar member 122 penetrates the motor shaft 186, and at its end extending therefrom, the right stabilizer bar member 122 penetrates the bottom of the flexible gear 192 as the output part of the reduction gear 172, and is connected to the bottom by serration engagement so as to be non-rotatable relative to the flexible gear 192 and non-movable relative to the axial direction. The ring gear 194 is generally ring-shaped with a plurality of teeth (slightly more than the number of teeth of the flexible gear 192, for example, two more) formed on its inner circumference, and is fixed to the housing 174. The peripheral wall of the flexible gear 192 is fitted onto the outside of the wave generator 190 and elastically deformed into an ellipse, meshing with the ring gear 194 at two points located in the major axis direction of the ellipse and not meshing with it at other points. When the wave generator 190 rotates once (360 degrees), that is, when the motor shaft 186 of the electric motor 170 rotates once, the flexible gear 192 and the ring gear 194 are rotated relative to each other by the difference in the number of teeth between them.

[0063] From the above configuration, when a force that relatively changes the distance between one of the left and right wheels 12 and the vehicle body and the distance between the other of the left and right wheels 12 and the vehicle body, i.e., a roll moment, acts on the vehicle body due to turning of the vehicle 10, a force that relatively rotates the left and right stabilizer bar members 122, 124, i.e., an external input to the actuator 130, acts. In this case, when the actuator 130 exerts a force that balances the external input as an actuator force due to a motor force (the electric motor 170 is a rotary motor, so it can be considered as a rotary torque, and therefore may be called a rotary torque) that is a force generated by the electric motor 170, the single stabilizer bar 120 formed by the two stabilizer bar members 122, 124 is twisted. The elastic force generated by this twisting becomes a force that opposes the roll moment, i.e., a roll restraining force. By changing the rotational position (operating position) of the actuator 130 by the motor force, the relative rotational positions of the left and right stabilizer bar members 122, 124 are changed, and the roll restraining force is changed, making it possible to change the amount of roll of the vehicle body. In this way, the present stabilizer device 114 is a device capable of changing the stabilizer rigidity.

[0064] The actuator 130 is provided with a motor rotation angle sensor 196 in the housing 174 for detecting the rotation angle of the motor shaft 186, i.e., the motor rotation angle ψ which is the rotation angle of the electric motor 170. In this actuator 130, the motor rotation angle sensor 196 is mainly an encoder, and the motor rotation angle ψ is used for controlling the actuator 130, i.e., for controlling the stabilizer device 114, as an index of the relative rotation angle (relative rotation position) of the left and right stabilizer bar members 122, 124, in other words, the amount of operation or rotation of the actuator 130.

[0065] As shown in FIG. 8, the electric motor 170 of the actuator 130 is supplied with power from a battery 66. In this stabilizer system, a converter 64 for boosting the voltage supplied by the battery 66 is provided, and the converter 64 and the battery 66 constitute a power supply. A stabilizer electronic control unit (hereinafter, may be simply referred to as a "stabilizer ECU") 140 is provided between the converter 64 and the two stabilizer devices 114. Although not shown in the drawings, the stabilizer ECU 140 is configured to include two inverters as drive circuits for the electric motors 170 and a computer equipped with a CPU, ROM, RAM, etc., and functions as a controller for controlling the actuator 130. The electric motor 170 of each of the two stabilizer devices 114 is supplied with power via an inverter included in the stabilizer ECU 140. Since the electric motor 170 is driven at a constant voltage, the amount of power supplied is changed by changing the amount of current supplied, and the electric motor 170 exerts a force according to the amount of current supplied. The amount of current supplied is changed by changing the ratio (duty ratio) between the pulse-on time and the pulse-off time by the inverter using PWM (Pulse Width Modulation).

[0066] Explaining with reference to FIG. 8, the stabilizer ECU 140 includes, in addition to the motor rotation angle sensor 196, an operation amount sensor 92 for detecting an operation amount (operation angle) δ of the steering wheel 16, which is a steering operation member, an actual lateral acceleration Gy that is a lateral acceleration Gy that is actually generated on the vehicle body, and R The stabilizer ECU 140 is further connected to a lateral acceleration sensor 198 provided for each of the four wheels 12 to detect the respective wheel speeds v W A wheel speed sensor 94 for detecting the vehicle speed v is connected to the stabilizer ECU 140, and the computer of the stabilizer ECU 140 detects the vehicle speed v based on the detection values ​​of the wheel speed sensors 94.

[0067] (b) Active stabilizer system control As described above, this stabilizer system includes two stabilizer devices 114, one for the front wheels and one for the rear wheels, and the stabilizer ECU 140, which is a controller, controls each of the two stabilizer devices 114 individually according to the set roll stiffness distribution. As described above, the two stabilizer devices 114 have roughly the same structure, and the control of each of the two stabilizer devices 114 is also roughly the same. In view of this, the following description will be given of the control of one stabilizer device 114, regardless of whether it is the front wheel side or the rear wheel side.

[0068] i) Basic Control The stabilizer ECU 140 determines a target rotational position of the actuator 130 based on a roll moment index amount that indicates the roll moment applied to the vehicle body, and controls the rotational position of the actuator 130 to be the target rotational position. The rotational position of the actuator 130 means the amount of operation of the actuator 130, and means the amount of rotation from the neutral position when a state in which no roll moment acts on the vehicle body is taken as a reference state and the rotational position of the actuator 130 in the reference state is taken as the neutral position. In other words, it means the amount of displacement of the operation position of the actuator 130 relative to the neutral position. In addition, since there is a corresponding relationship between the rotational position of the actuator 130 and the motor rotational angle that is the rotational angle of the electric motor 170, in actual control, the motor rotational angle ψ is used instead of the rotational position of the actuator 130. More specifically, the actuator 130 is an electric actuator for changing the posture of the vehicle 10, more specifically, the roll posture of the vehicle body, and the stabilizer ECU 140 as a controller controls the amount of operation of the actuator 130, i.e., the motor rotation angle ψ of the electric motor 170, as a controlled object.

[0069] To explain the control of the stabilizer device 114 more specifically, the lateral acceleration Gy as the roll moment index amount is a factor that changes the posture of the vehicle 10, and the stabilizer ECU 140 determines a target motor rotation angle ψ* as a target value of the motor rotation angle ψ to obtain an appropriate stabilizer stiffness based on the lateral acceleration Gy. More specifically, the stabilizer ECU 140 determines a target motor rotation angle ψ* as a target value of the motor rotation angle ψ based on the operation amount δ of the steering wheel 16 detected by the operation amount sensor 92 and the wheel speed v of each wheel 12 detected by the wheel speed sensor 94. W The lateral acceleration Gy is estimated based on the vehicle speed v ... E "), this estimated lateral acceleration Gy E and the actual lateral acceleration Gy detected by the lateral acceleration sensor 198. R Based on the above, the control lateral acceleration Gy is used for the control. * is determined according to the following formula: Gy * =K E Gy E +K R Gy R K E ,K R :Weighting factor

[0070] The stabilizer ECU 140 determines the control lateral acceleration Gy * Based on this, the target motor rotation angle ψ * Specifically, the control lateral acceleration Gy * The target motor rotation angle ψ * On the other hand, the stabilizer ECU 140 detects an actual motor rotation angle ψ, which is an actual value of the motor rotation angle ψ, by the rotation angle sensor 196. The stabilizer ECU 140 determines a target motor rotation angle ψ * Based on the motor rotation angle deviation Δψ, which is the deviation of the actual motor rotation angle ψ from S Specifically, the supply current I is determined according to the following formula, which is similar to the formula for the steering system:S Determine. I S =K P Δψ+K D dΔψ / dt+K I ∫Δψdt The stabilizer ECU 140 then determines the supply current I S Based on this, a current is supplied to the electric motor 170 via an inverter.

[0071] ii) Current reduction process In the present stabilizer system, in consideration of energy saving and power saving, a current reduction process is performed under specific circumstances on the current supplied to the actuator 130. The contents of the current reduction process in the present stabilizer system will be described below.

[0072] In this stabilizer system, similarly to the above-mentioned steering system, taking into consideration the responsiveness of the actuator 130, the stabilizer ECU 140 determines whether the vehicle speed v of the vehicle 10 is greater than or equal to the threshold vehicle speed v TH When the vehicle speed is equal to or lower than the predetermined speed (for example, 20 to 30 km / h) and when the vehicle 10 is being driven autonomously, the situation is recognized as a specific situation, and a current reduction process is performed.

[0073] In this stabilizer system, unlike the above steering system, low-pass filter processing is not performed on the target actuator movement amount as a current reduction process, but the supply current I according to the feedback control method is S In determining the proportional gain K P , Differential term gain K D However, in this stabilizer system, only the gain reduction process is performed to reduce the proportional term gain K P , Differential term gain K D For high gain K PH ,High Gain K DH and low gain K PL ,Low Gain K DL The stabilizer ECU 140 simply sets the proportional term gain K P, Differential term gain K D In other cases, high gain K PH ,High Gain K DH In particular, low gain K PL ,Low Gain K DL In other words, unlike the above steering system, the proportional gain K P , Differential term gain K D Depending on the vehicle speed v, high gain K PH ,High Gain K DH and low gain K PL ,Low Gain K DL Even with the current reduction process as described above, it is possible to sufficiently achieve energy saving and electricity saving in this stabilizer system.

[0074] Although detailed description will be omitted, the present stabilizer system also performs current reduction processing by reducing the target motor rotation angle ψ * may be subjected to a low-pass filter process similar to the low-pass filter process in the steering system. P , Differential term gain K D Depending on the vehicle speed v, high gain K PH ,High Gain K DH and low gain K PL ,Low Gain K DL The temperature may be gradually changed between 0.25 and 1.0.

[0075] In the above steering system, the functions of the steering ECU 20, which is the controller, are explained using a block diagram. However, since the functions of the stabilizer ECU 140, which is the controller of this stabilizer system, are similar, an explanation using a block diagram will be omitted.

[0076] iii) Control Flow The control of the stabilizer device 114 described above is performed by the computer of the stabilizer ECU 140 repeatedly executing a stabilizer control program shown in the flowchart of Fig. 11 at short intervals (for example, several to several tens of msec). Below, the flow of processing according to the stabilizer control program will be briefly described with reference to the flowchart.

[0077] In the process according to the stabilizer control program, first, in S21, the wheel speed v of each wheel 12 detected by the wheel speed sensor 94 is detected. W Based on the vehicle speed v, the vehicle speed v of the vehicle 10 is estimated, and in S22, the operation amount δ of the steering wheel 16 is detected via the operation amount sensor 92. Based on the vehicle speed v and the operation amount δ, in S23, the estimated lateral acceleration Gy E In the next step S24, the actual lateral acceleration Gy is estimated by the lateral acceleration sensor 198. R is detected, and in S25, the estimated lateral acceleration Gy E and actual lateral acceleration Gy R Based on the above, the control lateral acceleration Gy * is determined.

[0078] In the next step S26, the determined controlled lateral acceleration Gy * Based on this, the target motor rotation angle ψ * is determined, and in S27, the actual motor rotation angle ψ is detected by the rotation angle sensor 196.

[0079] In S28, it is determined whether the vehicle 10 is being driven automatically. If the vehicle 10 is being driven manually, in S29, the vehicle speed v is equal to or lower than the threshold vehicle speed v TH It is determined whether the vehicle speed v is equal to or less than the threshold vehicle speed v TH If it is determined that the proportional gain K P , Differential term gain K D However, high gain K PH ,High Gain K DHOn the other hand, when the vehicle is being driven automatically and when it is determined in S29 that the vehicle speed v is equal to or lower than the threshold vehicle speed, the proportional term gain K P , Differential term gain K D However, low gain K PL ,Low Gain K DL is set to.

[0080] Then, in S32, the target motor rotation angle ψ * The motor rotation angle deviation Δψ, which is the deviation of the actual motor rotation angle ψ relative to the P , Differential term gain K D , integral term gain K I Based on this, the supply current I to the electric motor 170 of the actuator 130 is calculated by the above method according to the PID feedback control law. S The supply current I S In step S33, the signal is supplied via an inverter, and one execution of the stabilizer control program is completed.

[0081] [3] Active suspension system (third embodiment) An active suspension system (hereinafter, sometimes simply referred to as a "suspension system"), which is a vehicle behavior control system according to the third embodiment, will be described below. This suspension system is mounted on a vehicle 10 on which the above-mentioned steering system and the above-mentioned stabilizer system are mounted.

[0082] (a) Configuration of active suspension system 12, the suspension system of the third embodiment is configured to include four suspension devices 220 provided corresponding to the four wheels 12 on the front, rear, left and right sides, and a control system responsible for controlling those suspension devices 220. The suspension devices 220 for the front wheels, which are steerable wheels, and the suspension devices 220 for the rear wheels, which are non-steerable wheels, can be considered to have substantially the same configuration except for the mechanism that enables the wheels 12 to be steered, so the configuration of the suspension devices 220 will be explained by representatively describing the suspension device 220 for the rear wheels.

[0083] i) Configuration of the suspension device As shown in Fig. 13, the suspension device 220 is an independent suspension type, and is a multi-link suspension device. The suspension device 220 includes a first upper arm 230, a second upper arm 232, a first lower arm 234, a second lower arm 236, and a toe control arm 238, each of which is a suspension arm. One end of each of the five arms 230, 232, 234, 236, and 238 is rotatably connected to the vehicle body, and the other end is rotatably connected to an axle carrier 240 that rotatably holds the wheel 12. The five arms 230, 232, 234, 236, and 238 allow the axle carrier 240 to move up and down along a fixed trajectory relative to the vehicle body.

[0084] The suspension device 220 includes two compression coil springs 246, 248 arranged in series, an electromagnetic actuator (hereinafter sometimes simply referred to as "actuator") 250 which is an electric actuator, and a hydraulic damper 252. The two coil springs 246, 248 cooperate with each other to function as a suspension spring that elastically connects the sprung portion and the unsprung portion. The actuator 250 also functions as a shock absorber, and is disposed between a mount portion 254 provided on the tire housing which is a component of the sprung portion, and a second lower arm 236 which is a component of the unsprung portion.

[0085] ii) Configuration of the electromagnetic actuator 14, the actuator 250 provided in each suspension device 220 is configured to include an outer tube 260 and an inner tube 262 that fits into the outer tube 260 and protrudes upward from the upper end of the outer tube 260. As will be described in detail later, the outer tube 260 is connected to the second lower arm 236 via a connecting mechanism 264 that has a compression coil spring 248 as a component, and the inner tube 262 is connected at its upper end to the mount portion 254.

[0086] The outer tube 260 is provided on its inner surface with a pair of guide grooves 266 extending in the axial direction of the actuator 250, while the inner tube 262 is provided with a pair of keys 268 at its lower end. The pair of keys 268 are fitted into the pair of guide grooves 266, respectively, and the keys 268 and guide grooves 266 prevent the outer tube 260 and the inner tube 262 from rotating relative to each other, but allow relative movement in the axial direction. Incidentally, a dust seal 270 is provided at the upper end of the outer tube 260 to prevent the intrusion of dust, mud, and the like from the outside.

[0087] The actuator 250 also has a hollow threaded rod 272 having an external thread, a nut 274 that holds a bearing ball and is screwed onto the threaded rod 272 , and an electric motor 276 .

[0088] The electric motor 276 is fixedly housed in a motor case 278, and a flange of the motor case 278 is fixed to the upper surface of the mount section 254, thereby being fixed to the mount section 254. The upper end of the inner tube 262, which is formed in a flange shape, is also fixed to the flange of the motor case 278, and the inner tube 262 is fixedly connected to the mount section 254 by such a structure.

[0089] A motor shaft 280, which is the rotating shaft of the electric motor 276, is a hollow shaft and is integrally connected to the upper end of the screw rod 272. In other words, the screw rod 272 is disposed inside the inner tube 262 with the motor shaft 280 extended, and a rotating force is applied to the screw rod 272 by the electric motor 276. Meanwhile, a support tube 282 is fixed to the bottom of the outer tube 260 in a state in which the screw rod 272 is housed therein, and a nut 274 is fixed to the upper end of the support tube 282. The screw rod 272 is screwed into the nut 274 fixed to the support tube 282, and the screw rod 272 and the nut 274 constitute a screw mechanism 284.

[0090] With the above-mentioned structure, the actuator 250 includes a sprung part side unit 286 including the inner tube 262, the motor case 278, the electric motor 276, the threaded rod 272, etc., and an unsprung part side unit 288 including the outer tube 260, the support tube 282, the nut 274, etc. In the actuator 250, the sprung part side unit 286 and the unsprung part side unit 288 move relative to each other in accordance with the relative movement between the sprung part and the unsprung part, and the threaded rod 272 and the electric motor 276 rotate. Furthermore, the actuator 250 generates an actuator force, which is a force for the relative movement between the sprung part side unit 286 and the unsprung part side unit 288, by applying a rotational force to the threaded rod 272 by the electric motor 276. Incidentally, this actuator force acts on the sprung part and the unsprung part via the compression coil spring 248.

[0091] iii) Damper configuration The damper 252 provided in each suspension device 220 is configured as a cylinder device, and is disposed between the actuator 250 and the second lower arm 236. The damper 252 has a generally cylindrical housing 290. The housing 290 is connected to the second lower arm 236 at a connecting portion 292 fixedly provided at the lower end thereof, and contains hydraulic fluid therein. A piston 294 is disposed inside the housing 290, and the piston 294 divides the interior of the housing 290 into two fluid chambers, an upper fluid chamber 296 and a lower fluid chamber 298, and is slidable relative to the housing 290.

[0092] The damper 252 also has a piston rod 300, which is connected at its lower end to the piston 294 and extends from the lid of the housing 290. The piston rod 300 passes through a hole provided in the bottom of the outer tube 260, and also passes through the threaded rod 272 and the motor shaft 280, and is fixed at its upper end to the motor case 278.

[0093] The damper 252 has a structure similar to that of a twin-tube shock absorber. To explain in more detail with reference to Fig. 15, the housing 290 has a double structure having an outer tube 302 and an inner tube 304, and a buffer chamber 306 is formed between the outer tube 302 and the inner tube 304. A partition wall 308 is provided near the bottom inside the housing 290, and an auxiliary liquid chamber 312 is formed which communicates with the buffer chamber 306 via a communication hole 310. In other words, the lower liquid chamber 298 and the buffer chamber 306 communicate with each other via the auxiliary liquid chamber 312.

[0094] The piston 294 is provided with a plurality of communication passages 314, 316 (two of each are shown in FIG. 15) that pass through it in the axial direction and communicate between the upper liquid chamber 296 and the lower liquid chamber 298. The piston 294 is also provided with disk-shaped valve members 318, 320 made of an elastic material on its lower and upper surfaces, respectively, with the valve member 318 closing the opening of the communication passage 314 on the lower liquid chamber 298 side, and the valve member 320 closing the opening of the communication passage 316 on the upper liquid chamber 296 side.

[0095] Similarly to the piston 294, the partition wall 308 is provided with a plurality of communication passages 322, 324 (two of each are shown in FIG. 15) that communicate between the lower liquid chamber 298 and the auxiliary liquid chamber 312. The partition wall 308 is provided with disk-shaped valve members 326, 328 made of an elastic material on its lower and upper surfaces, respectively, and the valve member 326 closes the opening of the communication passage 322 on the auxiliary liquid chamber 312 side, and the valve member 328 closes the opening of the communication passage 324 on the lower liquid chamber 298 side.

[0096] For example, when the piston 294 is moved upward in the housing 290, part of the hydraulic fluid in the upper fluid chamber 296 flows through the communication passage 314 to the lower fluid chamber 298, and part of the hydraulic fluid in the buffer chamber 306 flows into the lower fluid chamber 298 through the fluid passage 324. At that time, the hydraulic fluid deflects the valve members 318 and 328 and flows into the lower fluid chamber 298, thereby providing resistance to the upward movement of the piston 294. On the other hand, when the piston 294 is moved downward in the housing 290, part of the hydraulic fluid in the lower fluid chamber 298 flows through the communication passage 316 to the upper fluid chamber 296, and flows out through the fluid passage 322 to the buffer chamber 306. At that time, the hydraulic fluid deflects the valve members 320 and 326 and flows out of the lower fluid chamber 298, thereby providing resistance to the downward movement of the piston 294.

[0097] Due to the above-mentioned structure, the damper 252 allows the flow of hydraulic fluid between the upper fluid chamber 296 and the lower fluid chamber 298, and between the lower fluid chamber 298 and the buffer chamber 306 in accordance with the up and down movement of the piston 294 relative to the housing 290, and is provided with a flow resistance imparting mechanism that imparts resistance to that flow. In other words, the damper 252 generates resistance to the relative movement between the sprung and unsprung portions, i.e., a damping force against that relative movement.

[0098] iv) Configuration of suspension springs and linkage mechanisms A lower spring seat 340 is attached to the outer periphery of the housing 290 in the form of a flange. Meanwhile, an intermediate spring seat 342 is attached to the outer periphery of the outer tube 260 in the form of a flange. The compression coil spring 248 is disposed in a compressed state, sandwiched between the lower spring seat 340 and the intermediate spring seat 342. Furthermore, an upper spring seat 346 is attached to the lower surface of the mount portion 254 via a vibration isolating rubber 344. The compression coil spring 246 is disposed in a compressed state, sandwiched between the intermediate spring seat 342 and the upper spring seat 346.

[0099] With this structure, the compression coil spring 246 functions as a connecting spring that elastically connects the sprung part and the unsprung part-side unit 288, and the compression coil spring 248 functions as a support spring that elastically supports the unsprung part-side unit 288 on the unsprung part. Therefore, the compression coil spring 246 and the compression coil spring 248 work together to function as a suspension spring that elastically connects the sprung part and the unsprung part, and the compression coil spring 248 is a component of the connecting mechanism 264 that elastically connects the unsprung part and the unsprung part-side unit 288.

[0100] That is, in the present suspension device 220, the sprung part side unit 286 of the actuator 250 is a fixed unit that is fixedly connected to the sprung part, which is the unit fixed part, while the unsprung part side unit 288 is a floating unit that is floatingly supported by the unsprung part, which is the unit floating support part. Incidentally, in the present suspension device 220, the unsprung part side unit 288 is also floatingly supported by the compression coil spring 246 with respect to the sprung part.

[0101] The connecting mechanism 264 allows the unsprung side unit 288 to move relative to the unsprung part, but the relative displacement between the unsprung side unit 288 and the unsprung part during this relative movement is limited by a relative displacement limiting mechanism 350 included in the connecting mechanism 264. The relative displacement limiting mechanism 350 is composed of the bottom of the outer tube 260, an upper end of a housing 290 of the damper 252, a cylindrical skirt 352 attached to the bottom of the outer tube 260, a locking ring 354 attached to the outer periphery of the housing 290, etc.

[0102] Specifically, when the unsprung side unit 288 approaches the unsprung part, the bottom of the outer tube 260 abuts against the upper end of the housing 290 of the damper 252 via the cushion rubber 356, thereby restricting the approach. On the other hand, when the unsprung side unit 288 moves away from the unsprung part, the lower end formed in an inner flange shape of the skirt 352 abuts against the locking ring 354 via the cushion rubber 358, thereby restricting the separation.

[0103] v) Control system configuration As shown in FIG. 12, the suspension system of this embodiment is provided with a suspension electronic control unit 370 (hereinafter, sometimes abbreviated as "suspension ECU 370") which is a controller for controlling the operation of the four actuators 250, more specifically, the actuator force of each actuator 250 as a control target. The suspension ECU 370 is mainly configured with a computer equipped with a CPU, ROM, RAM, etc., and includes four inverters which are drive circuits for the electric motors 276 of the respective actuators 250. Each of the inverters is connected to the battery 66 which is a power source via a converter 64, and is connected to the electric motor 276 of the corresponding actuator 250. Each electric motor 276 is a DC brushless motor and is driven at a constant voltage. The actuator force of each actuator 250 is controlled by controlling the current flowing through each electric motor 276. The current control is performed by changing the ratio (duty ratio) between the pulse on time and the pulse off time in PWM (Pulse Width Modulation). Incidentally, the rotation angle φ of each electric motor 276 is detected by a motor rotation angle sensor 378, and the inverter controls the operation of each electric motor 76 based on the detected motor rotation angle φ.

[0104] In addition to the four motor rotation angle sensors 378, the suspension ECU 370 also includes an operation amount sensor 92 for detecting an operation amount (operation angle) δ of the steering wheel 16, which is a steering operation member, and an actual lateral acceleration Gy, which is a lateral acceleration Gy actually generated in the vehicle body. R In addition, various sensors are connected to the four suspension devices 220, specifically, a sprung acceleration G U The sprung vertical acceleration sensor 386 detects the vertical acceleration of the unsprung part, and the unsprung acceleration G Land a stroke sensor 390 for detecting a stroke amount S corresponding to the sprung-unsprung distance. Four wheel speed sensors 94 are provided corresponding to the four wheels and connected to the suspension ECU 170, and the suspension ECU 370 is configured to detect a vehicle speed v, which is the traveling speed of the vehicle 10, based on the detection values ​​of the wheel speed sensors 94.

[0105] In the control system of this suspension system, the suspension ECU 370 controls the operation of each actuator 250, i.e., controls the actuator force of each actuator 250, by controlling the current supplied to the electric motor 276 of each actuator 250 based on signals from the various sensors etc. described above.

[0106] (b) Control of electromagnetic actuators In this suspension system, the suspension ECU 370 controls the actuators 250 of each of the four suspension devices 220 to execute the following two types of control. More specifically, it executes sprung vibration damping control for damping vibration of the sprung part, and vehicle body attitude change suppression control for suppressing pitch and roll of the vehicle body. In view of the significance of the vehicle body attitude change suppression control, the actuators 250 can be considered as electric actuators for changing the vehicle attitude. The four actuators 250 have substantially the same structure and function, and the control of the four actuators 250 can be considered to be the same. Therefore, the control of one actuator 250 of one suspension device 220 will be described below.

[0107] i) Spring mass vibration damping control A vibration model based on the actual device configuration of the suspension device 220 (hereinafter, sometimes referred to as the "actual device model") is shown in Fig. 16(a). This vibration model is based on the inertial mass of the sprung part, that is, the sprung mass M U and the inertial mass of the unsprung part, ML In addition to the above, there is an intermediate mass M which serves as an inertial mass (to be described later) for the operation of the unsprung unit 288 of the actuator 250. I In this model, the sprung mass M U and unsprung mass M L Between them, a damper equivalent to the damper 252, i.e., a damping coefficient of C 1 Damper C 1 Also, the sprung mass M U and intermediate mass M I Between them, a spring equivalent to the compression coil spring 246, i.e., a spring having a spring constant of K 1 Spring K 1 , and an actuator A corresponding to the actuator 250 are arranged in parallel to each other. I and unsprung mass M L Between them, a spring equivalent to the compression coil spring 248, i.e., a spring having a spring constant of K 2 Spring K 2 is provided, and the unsprung mass M L Between the tire and the road surface, there is a spring equivalent to the tire, that is, a spring constant K 3 Spring K 3 are provided.

[0108] On the other hand, a control model, which is a theoretical model for controlling the actuator 250, is, for example, as shown in FIG. 16(b). In this model, the sprung mass M U But the damping coefficient is C S Skyhook Damper C S In other words, the control model is based on the skyhook damper theory.

[0109] For sprung mass vibration damping control, Skyhook Damper C S According to the above control model, the actuator force generated by the actuator A in the real device model is expressed by the skyhook damper C in the control model. SMore specifically, the actuator 250 is controlled so that the damping force generated by the sprung vertical acceleration sensor 386 corresponds to the vertical acceleration G U (Hereinafter, "Spring acceleration G U ") is the operating speed (absolute speed) of the sprung part, which is the sprung part speed v U is calculated, and the actuator force, i.e., its sprung velocity v U The actuator force of the magnitude according to the sprung mass vibration damping component F U The operation of the electric motor 276 is controlled so as to generate the F U =C S ·v U

[0110] By the way, the damping coefficient C S can be considered as a control gain, and is set to a value suitable for effectively damping vibrations at the sprung resonance frequency and frequencies in the vicinity thereof. In this suspension system, the resonance phenomenon of the unsprung portion is dealt with by the damper 252. That is, the damper C in the above-mentioned actual device model and control model 1 The damping coefficient C 1 That is, the damping coefficient of the damper 252 is set to a value suitable for effectively damping vibrations at the unsprung resonance frequency and frequencies in the vicinity thereof.

[0111] ii) Vehicle attitude change suppression control In this suspension system, in addition to the sprung mass vibration damping control, vehicle body attitude change suppression control is executed to reduce the roll of the vehicle body caused by turning of the vehicle and the pitch of the vehicle body caused by acceleration and deceleration of the vehicle. In the vehicle body attitude change suppression control, a force counteracting the roll moment acting on the vehicle body as a cause of the roll of the vehicle body and a force counteracting the pitch moment acting on the vehicle body as a cause of the pitch of the vehicle body are generated by the actuator 250.

[0112] More specifically, with respect to the roll of the vehicle body, the actuators 250 of the two suspension devices 220 on the inside wheel side of the turn apply an actuator force in a direction in which the sprung part and the unsprung part approach each other (hereinafter sometimes referred to as the "bound direction") in accordance with the roll moment, while the actuators 250 of the two suspension devices 220 on the outside wheel side of the turn apply an actuator force in a direction in which the sprung part and the unsprung part move away from each other (hereinafter sometimes referred to as the "rebound direction"). R (a type of postural change inhibitor)

[0113] Specifically, the estimated lateral acceleration Gy is estimated based on the steering amount δ of the steering wheel 16 and the vehicle speed v by a method similar to that used in the stabilizer system described above. E and the actual lateral acceleration Gy detected by the lateral acceleration sensor 198. R Based on this, the control lateral acceleration Gy * is determined according to the following formula: Gy * =K E Gy E +K R Gy R K E ,K R :Weighting factor The control lateral acceleration Gy determined in this way * is a roll moment index that indicates the roll moment acting on the vehicle body, and its control lateral acceleration Gy * Based on this, the roll suppression component F R is determined. F R =K Y Gy * (K Y : Roll suppression gain)

[0114] Roll suppression component F Ris one component of the actuator force and is the control target of the actuator 250. The lateral acceleration Gy is a factor that changes the attitude of the vehicle 10. As described above, the suspension ECU 370 determines the roll suppression component F as a target value of the control target based on the lateral acceleration Gy, which is a factor that changes the attitude of the vehicle 10. R Determine.

[0115] More specifically, with respect to the pitch of the vehicle body, in response to the nose dive of the vehicle body that occurs when the vehicle body is braked, an actuator force in the rebound direction is applied to each actuator 250 of the two suspension devices 220 on the front wheel side, and an actuator force in the bound direction is applied to each actuator 250 of the two suspension devices 220 on the rear wheel side, in accordance with the pitch moment. P In response to the pitch moment, the actuators 250 of the two suspension devices 220 on the rear wheel side generate an actuator force in the rebound direction, and the actuators 250 of the two suspension devices 220 on the front wheel side generate an absorber force in the bound direction, as a pitch suppression component F P (Posture change suppression component) is generated.

[0116] Specifically, the actual longitudinal acceleration Gx, which is the longitudinal acceleration Gx detected by the longitudinal acceleration sensor 384, is adopted as the pitch moment index amount that indicates the pitch moment, and the pitch suppression component F P is determined according to the following formula: F P =K X ·Gx (K X :Pitch suppression gain)

[0117] Pitch suppression component F Pis also a component of the actuator force and is an object of control by the actuator 250. The longitudinal acceleration Gx is also a factor that changes the attitude of the vehicle 10. As described above, the suspension ECU 370 determines the pitch suppression component F as a target value of the object of control based on the longitudinal acceleration Gx, which is a factor that changes the attitude of the vehicle 10. P Determine.

[0118] iii) Integration of two controls The above-mentioned sprung mass vibration damping control and vehicle body attitude change suppression control are performed comprehensively, and the sprung mass vibration damping component F U , Roll suppression component F R , pitch suppression component F P are treated as a single entity. Specifically, their components F U ,F R ,F P are summed according to the following equation to determine the total actuator force F to be generated by actuator 250: F=F U +F R +F P

[0119] Each component F U ,F R ,F P The combined actuator force F is the actuator force that should be generated by each of the actuators 250 of the four suspension devices 20, and the operation of the electric motor 276 of each actuator 250 is controlled to generate that actuator force. Specifically, there is a roughly proportional relationship between the generated actuator force F and the current supplied to the electric motor 276 of the actuator 250, and the suspension ECU 370 controls the supply current I, which is the current to be supplied to the electric motor 276 of each actuator 250, based on the actuator force F that should be generated by each actuator 250. S Determine the supply current I S Based on this, current is supplied to the electric motors 276 via an inverter.

[0120] iv) Current reduction processing In this suspension system as well, in consideration of energy saving and power saving, a current reduction process is performed on the current supplied to the actuator 250, i.e., the current supplied to the electric motor 276, under specific conditions. The contents of the current reduction process in this suspension system will be described below.

[0121] In this suspension system, similarly to the steering system and the stabilizer system, taking into consideration the responsiveness of the actuator 250, the suspension ECU 370 determines whether the vehicle speed v of the vehicle 10 is greater than or equal to the threshold vehicle speed v TH When the vehicle speed is equal to or lower than the predetermined speed (for example, 20 to 30 km / h) and when the vehicle 10 is being driven autonomously, the situation is recognized as a specific situation, and a current reduction process is performed.

[0122] In this suspension system, the target of the current reduction process is the above-mentioned attitude change suppression component, specifically, the roll suppression component F R , pitch suppression component F P The sprung mass vibration damping component F U is not subject to the current reduction process. Also, unlike the above steering system, the gain reduction process described above is not performed, and only low-pass filtering is performed on the target operation amount of the actuator, that is, the roll suppression component F R , pitch suppression component F P However, this low-pass filter processing is applied only under a specific condition, and is not applied when the specific condition is not met. Also, the cutoff frequency f C The cutoff frequency f according to the vehicle speed v is not changed. C In other words, only under certain circumstances, the roll suppression component F R , pitch suppression component F P , the cutoff frequency f C is the low frequency f CL1 Even with this type of current reduction processing, it is still possible to achieve energy and electricity savings in this suspension system.

[0123] In addition, the low-pass filter process may be performed without using a cutoff frequency f C It is also possible to increase the cutoff frequency f C may be changed according to the vehicle speed v and the driving mode, similarly to the steering system described above.

[0124] In the above steering system, the function of the steering ECU 20 serving as the controller has been explained using a block diagram. However, since the function of the suspension ECU 370 serving as the controller of this suspension system can be easily inferred, an explanation using a block diagram will be omitted.

[0125] v) Control Flow The control of actuator 250 described above is performed by the computer of suspension ECU 370 repeatedly executing a suspension control program shown in the flowchart of Fig. 17 at short intervals (for example, several to several tens of msec). The flow of processing according to the suspension control program will be briefly described below with reference to the flowchart.

[0126] In the process according to the suspension control program, first, in step S41, the sprung acceleration G U is detected, and in S42, the sprung acceleration G U Based on the sprung velocity v U Next, in S43, the sprung speed v U and the damping coefficient C of the Skyhook damper S Based on the above, the sprung mass vibration damping component F U is decided.

[0127] Next, in S44, the control lateral acceleration Gy * This control lateral acceleration Gy *The determination of the control lateral acceleration Gy is performed by a process similar to the process of S21 to S25 of the stabilizer control program. * Based on this, in S45, the roll suppression component F R In the next step S46, the longitudinal acceleration Gx is detected by the longitudinal acceleration sensor 384, and in step S47, the pitch suppression component F is determined based on the detected longitudinal acceleration Gx. P is determined.

[0128] In S48, it is determined whether the vehicle 10 is being driven automatically. If the vehicle 10 is being driven manually, in S49, the vehicle speed v is determined to be equal to or lower than the threshold vehicle speed v TH If it is determined in S48 that the vehicle is being driven automatically, or if the vehicle speed v is equal to or lower than the threshold vehicle speed v in S49, the vehicle speed v is determined to be equal to or lower than the threshold vehicle speed v. TH If it is determined that the roll suppression component F R and pitch suppression component F P and the cutoff frequency f C is low frequency and f CL1s The low-pass filter process is then performed.

[0129] Next, in S51, the sprung mass vibration damping component F U and the roll suppression component F with or without low-pass filtering. R , pitch suppression component F P The total actuator force F to be generated is determined by adding the above and the current I to be supplied to the electric motor 276 of the actuator 250 based on the actuator force F. S Then, in S53, the supply current I S Based on this, current is supplied to the electric motor 276 via the inverter, and one execution of the suspension control program is completed. [Explanation of symbols]

[0130] Vehicle Steering System 10: Vehicle 12: Wheel 14: Steering device 16: Steering wheel (steering operation member) 18: Operation device 20: Steering electronic control unit (steering ECU) [controller] 24: Steering motor [electric motor] 28: Steering actuator [electric actuator] 400: Vehicle speed estimator 402: Target steering amount determiner 404: Low pass filter 406: Integral element 408: Proportional element 410: Proportional term gain multiplier 412: Differential term gain multiplier 414: Integral term gain multiplier 416: Differentiator 418: Integrator 420: Inverter δ: Operation amount θ: Steering amount [control target] Actual steering amount [actual value] θ * : Target steering amount [target value] Δθ: Steering amount deviation γ: Steering gear ratio I S :Steering current v:Vehicle speed v TH : Threshold vehicle speed K P : Proportional gain K PL :Low gain K PH :High Gain K D : Differential term gain K DL :Low gain K DH :High Gain K I : Integral term gain f C : Cutoff frequency f CL ,f CL1 ,f CL2 :low frequency f CH :High frequency T:Time constant Active Stabilizer System 114: Stabilizer device 120: Stabilizer bar 130: Actuator 140: Stabilizer electronic control unit (stabilizer ECU) [controller] 170: Electric motor ψ: Motor rotation angle [control target] [actual value] ψ * : Target motor rotation angle [Target value] Δψ: Motor rotation angle deviation Gy: Lateral acceleration I S :Supply current Active Suspension System 220: Suspension device 250: Electromagnetic actuator 276: Electric motor 370: Suspension electronic control unit (suspension ECU) [controller] Gx: Longitudinal acceleration v U :Spring velocity F:Actuator force FU :Sprung mass vibration damping component F R : Roll suppression component [control target] [target value] F P : Pitch suppression component [Control object] [Target value]

Claims

1. A steer-by-wire steering system comprising: a steering member operated by a driver; a reaction motor which applies a reaction force to the operation of the steering member; a steering device having an electric actuator for steering wheels; and a controller for causing the steering device to steer the wheels by controlling an amount of steering of the wheels corresponding to an amount of operation of the electric actuator, the system being configured to steer the wheels by a force generated by the electric actuator and mounted on a vehicle, The vehicle is capable of both manual and automated driving, The controller: A target steering amount, which is a target for the steering amount of the wheels, is determined based on the operation amount of the steering operation member during manual driving, and is obtained based on information from an automatic driving electronic control unit during automatic driving, and a current is supplied to the electric actuator based on the target steering amount; and A steering system configured to perform a current reduction process for reducing the current supplied to the electric actuator when the vehicle's traveling speed is equal to or lower than a set traveling speed during manual driving, and to perform the process regardless of the vehicle's traveling speed during automatic driving.

2. The controller, as the current reduction process, 2. The steering system according to claim 1, wherein the target steering amount is subjected to low-pass filter processing only when the current reduction processing is performed, or the cut-off frequency in the low-pass filter processing applied to the target steering amount is lowered compared to when the current reduction processing is not performed.

3. The controller: a current is supplied to the electric actuator by feedback control based on a deviation of an actual steering amount from the target steering amount, 3. The steering system according to claim 1, wherein the current reduction process is configured to reduce a gain in the feedback control.

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