Vehicle behavior control system

Abstract

The present application provides a vehicle behavior control system with high practicality. In a vehicle behavior control system having an electric actuator (28) mounted on a vehicle and used to change the attitude of the vehicle, such as a steering system, an active stability system, an active suspension system, etc., a target value (θ * ) of a control object of the electric actuator is determined based on at least one of an attitude (δ) that the vehicle should assume and a factor that changes the attitude of the vehicle, a current (I S ) is supplied to the electric actuator based on the target value, and in a specific condition, a current reduction process is performed to reduce the current supplied to the electric actuator. In the current reduction process, a low-pass filter process (404) performed on the target value, a gain reduction process that reduces the proportional term gain (K P ) and the differential term gain (K D ) in a PID feedback control, etc. can be adopted. Energy saving and power saving of the system are sought.​​​​​​​​

Description

Technical Field

[0001] This invention relates to a vehicle behavior control system for controlling the behavior of a vehicle. Background Technology

[0002] In recent years, most vehicles have adopted systems that use electric actuators to control vehicle behavior, such as steer-by-wire systems, active stability systems, and electromagnetic suspension systems. The pursuit of vehicle electrification necessitates energy efficiency 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 at the end of the steering range, that is, near the steering end.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-218553 Summary of the Invention

[0006] While the technology described in the aforementioned patent documents shows promising results in reducing the contact load on the stop at the steering end, it is difficult to say that it is sufficient in terms of energy saving. In other words, from an energy-saving perspective, there is still much room for improvement in the vehicle behavior control system, and its practicality can be enhanced through certain modifications. This invention was made in view of this actual situation, and its objective is to provide a highly practical vehicle behavior control system.

[0007] To address the aforementioned problems, the vehicle behavior control system of the present invention is a vehicle behavior control system comprising an electric actuator and a controller. The electric actuator is mounted on a vehicle and used to change the vehicle's posture. The controller controls the amount of motion of the electric actuator or the force generated by the electric actuator as the controlled object. The controller is configured to: determine a target value of the controlled object based on at least one of the posture the vehicle should adopt and factors that cause the vehicle's posture to change, and supply current to the electric actuator based on the target value; and, under specific conditions, perform a current reduction process to reduce the current supplied to the electric actuator.

[0008] Invention Effects

[0009] In the vehicle behavior control system of the present invention, through the aforementioned current reduction process, the supply current to the electric actuator is reduced under specific conditions compared to non-specific conditions, thus a relatively large energy-saving effect can be expected. As a result, the vehicle behavior control system of the present invention becomes a highly practical vehicle behavior control system.

[0010] Invention scheme

[0011] The vehicle behavior control system that is the subject of this invention only needs to have an electric actuator (hereinafter, sometimes simply referred to as "actuator") for changing the vehicle's posture and a controller for controlling the actuator's actuation or the force generated by the actuator (hereinafter, sometimes referred to as "actuator force") as the controlled object. There are no particular limitations on its specific structure, function, or application. For example, an actuator driven by an electric motor can be used. The "vehicle posture" changed by the actuator refers to pitch posture, roll posture (tilt in the longitudinal or transverse direction of the vehicle body, tilt in the width direction), and slip angle relative to the vehicle's direction of travel (turning direction and degree of turning), etc.

[0012] Specifically, the present invention can be applied to steering systems that turn wheels, active stability systems that have stabilizer bars to suppress body roll and can control the roll suppression force exerted by the stabilizer bars, and active suspension systems that impart forces to the body and wheels in the direction of bounce and rebound and can control such forces.

[0013] More specifically, when the vehicle behavior control system of the present invention is a steering system, this steering system can also be a system that assists the driver's steering operation force through the force generated by the electric actuator, that is, a so-called power steering system. Furthermore, it can also be a system that turns the wheels through the force generated by the actuator without relying on the driver's steering operation force, that is, a so-called steer-by-wire system (hereinafter sometimes referred to as a "steer-by-wire system"). In the case of a steer-by-wire system, generally speaking, the amount of actuator actuation and the amount of wheel rotation have a specific relationship; therefore, the amount of actuator actuation can be used as the control object of the controller. Furthermore, the controller uses the amount of operation of steering components such as the steering wheel as an indicator of the posture the vehicle should adopt, determines the amount of wheel rotation based on this amount of operation, that is, the target value of the actuator actuation, and supplies current to the actuator based on this target value.

[0014] In the case where the vehicle behavior control system of the present invention is an active stability system, the actuator becomes an actuator for changing the roll posture of the vehicle body. Specifically, when the vehicle is equipped with a stabilizer bar with its two ends connected to the left and right wheels respectively and used to suppress the roll of the vehicle body, the configuration is such that the roll suppression force exerted by the stabilizer bar can be changed. In this case, when the roll suppression force exerted by the stabilizer bar depends on the actuator's actuation amount, the controller's control object is set to the actuation amount; when the roll suppression force exerted by the stabilizer bar depends on the actuator force, the controller's control object is set to the actuator force. Then, the controller takes the lateral acceleration generated by the vehicle body, the yaw rate of the vehicle body, the vehicle speed (hereinafter, sometimes referred to as "vehicle speed"), the lateral force acting on the vehicle body, etc., as factors that cause changes in the vehicle's posture, determines the actuator's actuation amount or the target value of the actuator force based on the lateral acceleration, etc., and supplies current to the actuator based on the target value.

[0015] In the case where the vehicle behavior control system of the present invention is an active suspension system, the actuator becomes an actuator for changing the pitch, roll, and bounce posture of the vehicle body, in other words, the relative distance (hereinafter sometimes referred to as "travel") between each wheel and the vehicle body in the vertical direction. When the actuator force is configured to act directly between the wheel and the vehicle body, this actuator force can be used as the control object of the controller. The actuator force can also function as a damping force for the relative movement between the vehicle body and the wheel, and further, it can function as a force for directly changing the travel amount (hereinafter sometimes referred to as "travel amount changing force"). In other words, the actuator force can also function as a force obtained by combining the damping force component and the travel amount changing force component. For example, when the actuator is an actuator for changing the pitch and roll posture of the vehicle body, the actuator force, specifically the travel amount changing component of the actuator force, can be used as the control object of the controller. Then, the controller takes the front-to-back acceleration and lateral acceleration acting on the vehicle body as factors that cause changes in the vehicle's posture. Based on these front-to-back acceleration and lateral acceleration, it determines the target value of the actuator force. Specifically, it determines the target value of the actuator force stroke change component and supplies current to the actuator based on this target value.

[0016] In the vehicle behavior control system of the present invention, the aforementioned current reduction process is performed under specific conditions. Since this vehicle behavior control system is for controlling the behavior of a vehicle, it is expected that by reducing the current supplied to the actuator, the responsiveness of the system related to this control, i.e., the responsiveness of the actuator's operation, will decrease. In short, it is expected that a certain amount of time will pass before the actuator's action amount and force reach a predetermined action amount and force. Therefore, ideally, for the current reduction process, it is desirable to consider a situation where high responsiveness of the actuator is not required as a specific condition, and perform the current reduction process under this condition. Specifically, for example, considering that high responsiveness of the system is generally not required at low vehicle speeds, the current reduction process can be performed when the vehicle speed is below a set speed, considering this as the aforementioned specific condition. Furthermore, for example, when the vehicle is designed to operate in both manual and automatic driving modes by a driver, it is generally desirable to consider that the vehicle operation requiring high responsiveness is not performed during automatic driving; simply put, to avoid some degree of over-exertion, the current reduction process can be performed when driving in automatic driving mode, considering this as the aforementioned specific condition.

[0017] There are no particular restrictions on the method to be followed when performing current reduction processing, but for example, the controller can perform current reduction processing in the manner described below.

[0018] As explained earlier, the controller determines the target value of the controlled object. Current reduction is performed according to a method, thus the controller can be configured to either apply low-pass filtering to the target value only under specific conditions, or, under specific conditions, reduce the cutoff frequency of the low-pass filtering applied to the target value compared to other conditions. The low-pass filter introduces a delay to the output of the target value, suppressing abrupt changes in the target value. Furthermore, by reducing the cutoff frequency of the low-pass filter, the rate of change of the target value can be further slowed. This method reduces the current supplied to the actuator.

[0019] The controller can be configured to supply current to the actuator via feedback control based on the deviation of the actual value of the controlled object from the target value. In this configuration, current reduction processing is performed according to another method, so the controller can also be configured to reduce the gain in the feedback control under specific conditions compared to conditions other than those specific. This method reduces the current supplied to the actuator. Furthermore, as explained in detail later, feedback control can be performed by adding the proportional, derivative, and integral components. In this case, the gain used to determine the proportional and derivative components, which contribute to the responsiveness, can also be reduced only during the current reduction processing.

[0020] It should be noted that in the current reduction process, either one of the two methods mentioned above can be used, or both methods can be used. Attached Figure Description

[0021] Figure 1 This is a diagram showing the overall configuration of the vehicle steering system as a vehicle behavior control system according to the first embodiment.

[0022] Figure 2 It is an overall view of the steering actuator that constitutes the steering system of a vehicle, and a cross-sectional view of the part equipped with the steering quantity sensor.

[0023] Figure 3 This is a cross-sectional view of the steering actuator used to illustrate the steering motor and the motion conversion mechanism.

[0024] Figure 4 It is a graph representing the mapping data used to determine or set the steering gear ratio based on vehicle speed, the cutoff frequency in low-pass filtering, and the proportional and differential gain used to determine the steering current.

[0025] Figure 5 This is a block diagram illustrating the functions of the electronic steering control unit.

[0026] Figure 6 It is a graph used to illustrate the effect of low-pass filtering applied to a target steering input.

[0027] Figure 7 This is a flowchart of the steering control program executed in the electronic steering control unit.

[0028] Figure 8 This is a diagram showing the overall configuration of the active stability system as a vehicle behavior control system in the second embodiment.

[0029] Figure 9 This is a diagram showing the stabilization devices on the front and rear wheel sides that constitute the active stabilization system.

[0030] Figure 10 This is a cross-sectional view of the actuator of the stabilizing device.

[0031] Figure 11 This is a flowchart of the stability control program executed in the stabilizer's electronic control unit.

[0032] Figure 12 This is a diagram showing the overall configuration of the active suspension system as a vehicle behavior control system in the third embodiment.

[0033] Figure 13 This is a diagram showing the suspension components that make up an active suspension system.

[0034] Figure 14 This is a cross-sectional view showing the electromagnetic actuator of the suspension system.

[0035] Figure 15 This is a cross-sectional view showing the damper of the suspension system.

[0036] Figure 16 It is a conceptual diagram representing the actual device model and control model of the suspension system.

[0037] Figure 17 This is a flowchart of the suspension control program executed in the suspension electronic control unit.

[0038] Explanation of reference numerals in the attached figures:

[0039] <Vehicle Steering System>

[0040] 10: Vehicle; 12: Wheel; 14: Steering mechanism; 16: Steering wheel (steering operation component); 18: Operating device; 20: Steering electronic control unit (steering ECU) [controller]; 24: Steering motor [electric motor]; 28: Steering actuator [electric actuator]; 400: Vehicle speed estimation unit; 402: Target steering amount determination unit; 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: Converter; δ: Operational quantity; θ: Steering amount [controlled object] Actual steering amount [actual value]; θ * Target steering input (target value); Δθ: steering input deviation; γ: steering gear ratio; I S : Steering current; v: Vehicle speed; v TH Threshold 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

[0041] <Active Stabilization System>

[0042] 114: Stabilizer; 120: Stabilizer bar; 130: Actuator; 140: Stabilizer electronic control unit (Stabilizer ECU) [Controller]; 170: Electric motor; ψ: Motor rotation angle [Controlled object] [Actual value]; ψ * Target motor rotation angle (target value); Δψ: motor rotation angle deviation; Gy: lateral acceleration; I S Supply current

[0043] <Active Suspension System>

[0044] 220: Suspension system; 250: Electromagnetic actuator; 276: Electric motor; 370: Electronic control unit for suspension (suspension ECU) [controller]; Gx: Rear acceleration; v U : Sprout speed; F: Actuator force; F U : Vibration damping component of the upper part of the spring; F R : Roll suppression component [Controlled object] [Target value]; F P Pitch suppression component [Controlled object] [Target value]. Detailed Implementation

[0045] Hereinafter, as specific embodiments of the present invention, a vehicle steering system, an active stability system, and an active suspension system, as embodiments of the present invention, will be described in detail with reference to the accompanying drawings. It should be noted that, in addition to the embodiments described below, the present invention can also be implemented in various ways, based on the knowledge of those skilled in the art, with various modifications and improvements, as represented by the methods described in the [Inventive Solution] section.

[0046] [Example]

[0047] [1] Steering system for vehicles (first embodiment)

[0048] The following describes the vehicle steering system (hereinafter, sometimes simply referred to as "steering system") as a vehicle behavior control system according to the first embodiment.

[0049] (a) Composition of vehicle steering system

[0050] i) Overall composition

[0051] like Figure 1As schematically shown, this steering system is a steer-by-wire type steering system that turns the left and right wheels 12, which are the front wheels of the vehicle 10, respectively. It is generally configured to include: a steering device 14 for turning these wheels 12; an operating device 18 having a steering wheel 16 as a steering operating member operated by the driver; and a steering electronic control unit 20 (hereinafter, sometimes referred to as "steering ECU 20") as a controller for causing the steering device 14 to perform turning of the wheels 12 corresponding to the operation of the steering wheel 16.

[0052] Each wheel 12 is held rotatably by a steering knuckle (not shown), which is rotatably supported on the vehicle body via a suspension system. The steering mechanism 14 is configured to include: a steering actuator 28 having an electric motor, i.e., a steering motor 24, as a drive source, and being an electric actuator for moving the steering stick 26 left and right; and connecting rods 32, one end of which is connected to both ends of the steering stick 26 via ball joints 30. The other end of each connecting rod 32 is connected via ball joints (not shown) to a steering knuckle arm (not shown) located on the corresponding steering knuckle. By moving the steering stick 26 left and right, each steering knuckle rotates, and each wheel 12 is steered.

[0053] ii) Construction of the steering actuator

[0054] The steering actuator 28, which constitutes the steering device 14, is an actuator mounted on the vehicle 10 and used to change the attitude of the vehicle 10. Specifically, it is an actuator used to change the pointing (or orientation) of the vehicle 10 relative to the direction of travel; that is, it is an actuator used to change the slip angle of the vehicle 10. Regarding the basic structure of the steering actuator 28, if we also refer to... Figure 2 , Figure 3 To explain further, regarding the steering actuator 28, based on the description of its overall appearance... Figure 2 (a) indicates the interior of the rudder motor 24 and the rudder actuator 28. Figure 3 It is understood that within the housing 40, the rudder stock 26 is held in a position where it cannot rotate about its axis but can move left and right. A threaded groove 42 is formed on the outer periphery of the rudder stock 26. Furthermore, within the housing 40, the retaining sleeve 44 is held in a position where it can rotate about its axis but cannot move left and right. A nut 46, which retains the bearing balls, is fixedly held in the retaining sleeve 44. The nut 46 and the rudder stock 26 are screwed together, forming a ball screw mechanism. That is, it can be considered as forming a threaded mechanism including the thread on the rudder stock 26 and the nut 46 having a thread that engages with that thread.

[0055] The steering motor 24 is mounted outside the housing 40 with its axis parallel to the axis of the steering stick 26. A timing pulley 50 is attached to one end of the motor rotation shaft 48 (hereinafter sometimes simply referred to as "motor shaft 48"). Engaging teeth 52 are formed on the outer periphery of the retaining sleeve 44, similar to those on the timing pulley 50. The retaining sleeve 44 functions as another timing pulley paired with the timing pulley 50. A timing belt 54, serving as a transmission belt, is wound around the retaining sleeve 44 and the timing pulley 50. By rotating the steering motor 24 (strictly speaking, rotating the motor shaft 48), the nut 46 rotates, and the steering stick 26 moves in the left-right direction in the direction corresponding to the rotation of the steering motor 24. That is, a belt transmission mechanism is provided, which is configured to include a retaining sleeve 44, a timing pulley 50, and a timing belt 54. An action conversion mechanism 55 is provided through the belt transmission mechanism and the aforementioned threaded mechanism to convert the rotational motion of the motor shaft 48 into the action of the steering rod 26 corresponding to the amount of the rotational motion.

[0056] In this steering system, the steering motor 24 is a three-phase brushless DC motor. Specifically, magnets 56 are arranged circumferentially and fixedly disposed on the outer periphery of the motor shaft 48, and coils 58 are disposed opposite to these magnets 56 and held in the motor housing 59, which serves as the housing of the steering motor 24. The steering motor 24 is rotated by energizing the coils 58. The torque generated by the steering motor 24, i.e., the force that moves the rudder stick 26 left and right, is approximately proportional to the current supplied to the coils 58.

[0057] iii) Composition of the operating device

[0058] like Figure 1 As shown, the operating device 18 is configured to include: a steering wheel 16; a steering shaft 60, fixed to the steering wheel 16 and configured to rotate integrally with the steering wheel 16; and a reaction force motor 62 as an electric motor. The motor shaft of the reaction force motor 62 is integrated with the steering shaft 60, and the reaction force motor 62 imparts rotational torque to the steering wheel 16. This rotational torque functions as a reaction force (operational reaction force) for the operation of the steering wheel 16 performed by the driver, that is, a reaction force (operational reaction force) for steering operations. Therefore, the reaction force motor 62 becomes the motor constituting the reaction force actuator. Although detailed structural illustrations are omitted, the reaction force motor 62, like the steering wheel motor 24, is configured as a brushless DC motor. The operation reaction force is generated by energizing the reaction force motor 62, and its magnitude is approximately proportional to the current supplied to the reaction force motor 62. It should be noted that the operating reaction force also functions as a force to return the steering wheel 16 to the neutral position (a position where it is neither turned to the right nor to the left).

[0059] iv) Control-related components

[0060] The steering ECU 20, responsible for controlling the steering system, is configured to include: a computer, consisting of a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc.; and a converter, which is the drive circuit (driver) for the steering motor 24 and the reaction motor 62, respectively. Figure 1 As can be seen, the steering ECU 20, specifically, each converter of the steering ECU 20 is connected to the battery 66, which serves as a power source, via a converter 64, and supplies current based on computer commands to the steering motor 24 and the reaction force motor 62 respectively.

[0061] In the steering mechanism 14 and the operating mechanism 18, various sensors are provided 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 stick 26, that is, the left-right movement position of the steering stick 26, as the steering amount (steering angle) θ of the wheel 12. Referring to a cross-section showing the portion in the steering actuator 28 where this steering amount sensor 80 is located... Figure 2 (b) will be explained in detail here. A rack 82 is formed on the rudder stick 26, and a pinion shaft 86 with a pinion 84 meshing with the rack 82 is held in the housing 40. Furthermore, this rudder actuator 28 is an actuator used in a so-called power steering system, and the pinion shaft 86 is connected to the input shaft 90 via a torsion bar 88. In this steering system, when the rudder actuator 28 is used in a power steering system, a rudder displacement sensor 80 is installed at the location where a torque sensor for detecting steering torque is provided, instead of the torque sensor.

[0062] On the other hand, the operating 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 construction, so detailed descriptions are omitted here.

[0063] It should be noted that each wheel 12 is equipped with a wheel speed v for detecting the rotational speed of each wheel. W The wheel speed sensor 94 is used to estimate the vehicle speed v, which is the driving speed of the vehicle 10, based on the detection value of the wheel speed sensor 94.

[0064] Furthermore, this vehicle 10 is capable of autonomous driving. An autonomous driving switch 96 for performing autonomous driving is located on the instrument panel, as well as a driving mode selection switch 98 for switching driving modes. Although detailed descriptions are omitted, the driving modes are pre-configured as an ECO mode prioritizing fuel efficiency and a Sport mode for agile driving. The driving mode selection switch 98 is configured to switch between these two modes. The autonomous driving switch 96 and the driving mode selection switch 98 are also connected to the steering ECU 20.

[0065] (b) Control of vehicle steering system

[0066] In this steering system, the steering ECU 20, acting as the controller, specifically, controls the steering of the wheels 12 via the steering actuator 28 (hereinafter, sometimes referred to as "steering control") to control the slip angle of the vehicle 10. Furthermore, to impart a reaction force to the steering wheel 16 in response to the steering operation performed by the driver, reaction force control is performed on the operating device 18, specifically on the reaction force motor 62 of the operating device 18. This reaction force control is a general control, therefore its description is omitted here; the steering control will be described in detail below.

[0067] i) Basic steering control

[0068] In short, steering control is used to control the turning of the wheels 12 in response to a steering request. When the vehicle 10 is manually driven, the steering wheel 16 operation amount δ detected by the operation amount sensor 92 is a steering request, and the steering ECU 20 determines the target steering amount θ that becomes the steering amount θ of the wheels 12 based on this operation amount δ. * If described in detail, this steering system employs a variable gear ratio steering system (VGRS), with the steering ECU 20 based on the wheel speed v detected by the wheel speed sensor 94. W The vehicle speed v of vehicle 10 is estimated, and the steering gear ratio (the ratio of steering input θ to operating input δ) γ corresponding to that speed v is determined. The steering gear ratio γ is determined with reference to the mapping data stored in the steering ECU 20. Although detailed explanations are omitted, it is as follows... Figure 4 As shown in (a), the steering gear ratio γ is set such that the higher the vehicle speed v, the smaller the steering gear ratio γ becomes. Then, the steering ECU 20 determines the target steering amount θ according to the following formula. * .

[0069] θ * =γ·δ

[0070] On the other hand, when the vehicle 10 is put into autonomous driving mode by operating the autonomous driving switch 96, the steering ECU 20 obtains the target steering amount θ based on information sent from the autonomous driving electronic control unit (hereinafter, sometimes referred to as the "autonomous driving ECU"). Illustration omitted. * .

[0071] It should be noted that the steering input θ can be considered as the left-right movement of the steering stick 26, that is, the action of the steering actuator 28, which becomes the controlled object of the steering control of this steering system. Therefore, the target steering input θ * The target value becomes the controlled object. Additionally, in this steering system, the target steering input θ... * The rotational amount (rotational position) of the pinion shaft 86 of the steering actuator 28 is defined.

[0072] The steering ECU 20 detects the actual steering amount θ (hereinafter, sometimes referred to as "actual steering amount θ") via the steering amount sensor 80 of the steering actuator 28, and uses it as the actual value of the controlled object. The steering ECU 20 determines the actual steering amount θ relative to the target steering amount θ. * The deviation of the steering input Δθ is calculated, and based on this deviation Δθ, the current (hereinafter sometimes referred to as "steering current") supplied to the steering motor 24 is determined according to the feedback control method. S In detail, the steering current I is determined according to the following formula. S .

[0073] I S =K P ·Δθ+K D ·dΔθ / dt+K I ·∫Δθdt

[0074] The first, second, and third terms on the right-hand side of the above formula represent the proportional component, differential component, and integral component, respectively, K. P K D K I These are the proportional gain, derivative gain, and integral gain, respectively. The steering ECU20 determines the steering current I based on the above-described formula. S The current is supplied to the steering motor 24 via a converter.

[0075] ii) Current reduction processing

[0076] In this steering system, considering energy saving and power efficiency, the supply current to the steering actuator 28 is reduced under certain conditions. The details of this current reduction process will be explained below.

[0077] When the current supplied to the steering actuator 28 decreases, the force generated by the steering actuator 28 (hereinafter, sometimes referred to as the "actuator force") decreases, and the action of the steering actuator 28 may be delayed. That is, the responsiveness of the steering actuator 28 decreases. Specifically, in the steering of the wheel 12, changes in the actual steering amount θ may cause it to not follow the target steering amount θ. * Such a situation as the change in target steering angle θ. * When the change is large, in other words, when a relatively sharp steering operation is required, or when a larger actuator force is needed, this possibility increases.

[0078] Therefore, in this steering system, the specific situation for which current reduction processing is performed is limited to a situation where high responsiveness 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 wheel 12 increases, requiring a larger actuator force. Furthermore, from the viewpoint of vehicle handling feel and stability, a certain degree of high responsiveness is required. In view of these circumstances, when the vehicle speed v is low, specifically when the vehicle speed v is a threshold vehicle speed v... TH When the speed is below 20km / h to 30km / h, the steering ECU20 recognizes it as a specific situation and performs current reduction processing.

[0079] In this steering system, two current reduction processes with different methods are executed. One of the two current reduction processes is applied to the target steering amount θ. * The low-pass filtering process (hereinafter, sometimes simply referred to as "filtering") is implemented. If detailed, the steering ECU 20 determines the target steering amount θ as described above. * Enforcement prohibits frequencies higher than the cutoff frequency f. C Target rudder frequency θ * This kind of processing, in other words, makes it have a frequency higher than the cutoff frequency f. C Target rudder frequency θ * Changes in this process result in delayed processing. For example... Figure 4 As shown in graph (b), the cutoff frequency f C At vehicle speed v, the threshold vehicle speed v TH The following is set as a low frequency f. CL This vehicle 10 has two driving modes: an ECO mode that prioritizes fuel efficiency and a Sport mode that prioritizes vehicle handling performance. In the graph, the cutoff frequencies f for ECO mode and Sport mode are shown as solid and dashed lines, respectively. C The change in frequency f, as shown in the graph, indicates that considering the difference in the required level of responsiveness, the low-frequency f is set in ECO mode. CL1 To be used as low frequency fCL In sports mode, set the low frequency f CL2 (>f CL1 ) as a low rate f CL According to the graph, regardless of the driving mode, the cutoff frequency f C They are all set to increase as the vehicle speed v exceeds the threshold speed v TH And as it increases, the cutoff frequency f C As the speed gradually increases, at a certain speed v, the cutoff frequency f... C Set as high frequency f CH Additionally, for example, low frequency f CL1 It can be set to around 5Hz, low frequency f CL2 It can be set to around 10Hz, high frequency f CH It can be set to around 30Hz.

[0080] The other aspect of the two current reduction processes is the steering current I, which is controlled according to the feedback control method described above. S In the decision to reduce the gain K of the proportional term P Differential term gain K D The processing (hereinafter, sometimes referred to as "gain reduction processing"). Specifically, such as... Figure 4 As shown in the curve (c), at a vehicle speed v = threshold vehicle speed v TH The following is the proportional gain K related to responsiveness. P Differential term gain K D They were each set to low gain K PL Low gain K DL Furthermore, it is set to work as the vehicle speed v exceeds a threshold speed v. TH As it increases, the proportional gain K... P Differential term gain K D The gain K gradually increases, and at a vehicle speed v above a certain level, the proportional term gain K... P Differential term gain K D Set to high gain K PH High gain K DH .

[0081] Furthermore, as explained above, this vehicle 10 is pre-programmed to operate in both manual and automatic modes. In automatic mode, the vehicle 10 is configured to only allow for relatively slow steering. Considering this, the steering ECU 20 is configured to reduce current under specific conditions during automatic driving, regardless of the vehicle speed v.

[0082] In detail, although in the case of manual driving, the cutoff frequency f in the filtering process C Steering current I SThe gain K of the proportional term in the decision P Differential term gain K D As mentioned above, the cutoff frequency is set based on vehicle speed v, but in the case of autonomous driving, it is independent of vehicle speed v. C Set to low frequency f CL1 proportional term gain K P Differential term gain K D They were each set to low gain K PL Low gain K DL .

[0083] In this steering system, the target steering amount θ is adjusted even under non-specific conditions. * Filtering is performed, but it can also be omitted in situations other than specific ones. Furthermore, in this steering system, filtering and proportional term gain K are considered. P Differential term gain K D In the settings, when the vehicle speed v exceeds the threshold speed v TH At that time, the cutoff frequency f depends on the vehicle speed v. C Proportional term gain K P Differential term gain K D Set to low frequency f respectively CL Low gain K PL Low gain K DL It gradually rises to a high frequency f CH High gain K PH High gain K DH However, it could also be when the vehicle speed v exceeds the threshold speed v. TH When the cutoff frequency f is... C Proportional term gain K P Differential term gain K D The high frequency f is set in stages. CH High gain K PH High gain K DH Furthermore, in this steering system, as a current reduction process, the cutoff frequency f in the aforementioned filtering process is used. C Changes and steering current I S The gain K of the proportional term in the decision P Differential term gain K D Both parties can be changed, but it is also possible to change only one party.

[0084] iii) Functional block diagram related to steering control

[0085] If we illustrate the functions of the steering ECU20 related to the steering control, including the aforementioned current reduction process, using a block diagram, then it becomes... Figure 5That's right. The steering ECU 20 has a vehicle speed estimation unit 400, which is based on the individual wheel speeds v of the four wheels 12 obtained by the wheel speed sensors 94. W To estimate the vehicle speed v of the vehicle 10, the steering ECU 20 has a target steering amount determination unit 402, which, based on the vehicle speed v, determines the target steering amount according to... Figure 4 The steering gear ratio γ is determined using the mapping data shown in (a), and the target steering amount θ is determined based on the steering gear ratio γ and the steering wheel operation amount δ detected by the operation amount sensor 92. * .

[0086] Furthermore, the steering ECU20 has a low-pass filter 404, which filters the target steering amount θ determined by the target steering amount determination unit 402. * Low-pass filtering is performed. The low-pass filter 404 has a general configuration; for simplicity, it is configured to include an integrator 406 and a proportional element 408. The "a" in the proportional element 408 is defined by the following formula.

[0087] a = 1 / T

[0088] Where T: time constant

[0089] Furthermore, the transfer function G(s) of the low-pass filter 404 is calculated as follows.

[0090] G(s) = 1 / (1 + T·s)

[0091] Where s: Laplace operator

[0092] Furthermore, the time constant T and the cutoff frequency f C The relationship can be expressed by the following formula.

[0093] T = 1 / (2πf) C )

[0094] As described above, the low-pass filter 404, depending on whether the driving mode is automatic or manual, in the case of manual driving of vehicle 10, uses the estimated vehicle speed v as a reference. Figure 4 The cutoff frequency f is set using the mapping data shown in (b). C Furthermore, when vehicle 10 is in autonomous driving mode, the cutoff frequency f will be... C Set to low frequency f CL1 Then, based on the set cutoff frequency f C This determines the time constant T and performs filtering.

[0095] The steering ECU 20 determines the actual steering amount θ detected by the steering amount sensor 80 via the actuator 28 relative to the target steering amount θ that has been filtered. * The deviation is the steering deviation Δθ. The steering ECU 20 has a proportional gain multiplier 410, a differential gain multiplier 412, an integral gain multiplier 414, a differentiator 416, and an integrator 418. Based on the steering deviation Δθ, the proportional gain multiplier 410 determines the steering current I. S The proportional component, via differentiator 416 and differential term gain multiplier 412, determines the steering current I. S The differential component is used to determine the steering current I via integrator 418 and integral term gain multiplier 414. S The integral components are then added together by the steering ECU20 to determine the steering current I. S When determining the proportional and derivative components, the steering ECU 20 considers whether the vehicle is in automatic or manual driving mode. In the case of manual driving, it bases its decisions on the estimated vehicle speed v, referencing... Figure 4 The mapping data shown in (c) is used to determine the scaling factor gain K. P Differential term gain K D When vehicle 10 is in autonomous driving mode, the proportional gain K will be... P Differential term gain K D Set to low gain K respectively PL Low gain K DL Regarding the determined steering current I S The command is sent to the converter 420, which supplies the current to the steering motor 24 of the actuator 28.

[0096] iv) Effects obtained through current reduction processing

[0097] Next, refer to Figure 6 Specifically, regarding the effect obtained through current reduction processing, the effect achieved by reducing the steering angle θ relative to the aforementioned target is... * The effect of low-pass filtering is explained. Figure 6 of (a), Figure 6 The curves in (b) show the target steering amount θ over time t without filtering. * Changes in actual steering input θ and steering current I S Changes, Figure 6 (c) Figure 6 The curves (d) show the target steering amount θ over time t after filtering. * The actual change in steering input θ and steering current IS The change. It should be noted that the cutoff frequency f in the filtering process... C The frequency is set to 5Hz. With and without filtering, the steering conditions—namely, vehicle speed v, steering wheel 16 input δ, and operating speed dδ / dt—are set to the same. Furthermore, steering wheel 16 operation begins at time t0. Additionally, the steering motor 24 is a three-phase brushless motor with a steering current I... S The current of each of the U-phase, V-phase, and W-phase is shown.

[0098] according to Figure 6 As shown in curve (a), without filtering, the target steering angle θ * The gradient is relatively steep, and the actual steering input θ will not fully follow the target steering input θ. * On the other hand, according to Figure 6 As shown in the curve (c), when filtering is applied, the target steering angle θ * The gradient increase is relatively gentle, and the actual steering input θ will follow the target steering input θ quite well. * The result is that... Figure 6 Comparing the curves in Figure (b) and (d), it can be seen that the amplitude of the current in each phase decreases when filtering is implemented, compared to the case without filtering. That is to say, the rudder current I... S It is reduced due to the implementation of filtering.

[0099] v) Control Process

[0100] The steering control described above is repeatedly executed by the computer of the steering ECU20 at short time intervals (e.g., a few milliseconds to tens of milliseconds). Figure 7 The steering control procedure is represented by a flowchart. The following is a brief explanation of the process according to the steering control procedure, referring to the flowchart.

[0101] In the steering control procedure, firstly, in step 1 (hereinafter referred to as "S1"; the other steps are the same), it is determined whether the vehicle 10 is in automatic driving mode based on the operating state of the automatic driving switch 96. If it is not in automatic driving mode, that is, in manual driving mode, in S2, the automatic driving indicator FLAD is set to "0". The automatic driving indicator FLAD is a flag that is set to "0" when manually driving and set to "1" when in automatic driving mode.

[0102] In the subsequent S3, the wheel speed v of each wheel 12 is detected by the wheel speed sensor 94. WTo estimate the speed v of vehicle 10, in S4, based on the estimated speed v, refer to the above... Figure 4 The steering gear ratio γ is determined using the mapping data shown in (a). Then, in S5, the target steering amount θ is determined using the determined steering gear ratio γ according to the above formula. * .

[0103] If the system is determined to be in autopilot mode in S1, the autopilot flag FLAD is set to "1" in S6, and the target steering input θ is obtained based on information sent from the autopilot ECU in S7. * .

[0104] In the next step, S8, a determination is made based on the value of the automatic driving indicator FLAD. If the vehicle is being manually driven, in S9, the selected driving mode at the current time point is determined based on the operating state of the driving mode selection switch 98; that is, whether it is ECO mode or Sport mode. Then, in S10, based on the determined driving mode and vehicle speed v at the current time point, referencing... Figure 4 The mapping data shown in (b) is used to set the cutoff frequency f in the filtering process. C On the other hand, in the case of automated driving, in S11, the cutoff frequency f C Set to low frequency f CL1 Then, in S12, the determined target steering angle θ is... * Perform the low-pass filtering process as described above. The specific process of low-pass filtering performed in this program is a general one, so the explanation is omitted here.

[0105] In subsequent S13, the value of the automatic driving indicator FLAD is determined again. In the case of manual driving, in S14, based on the vehicle speed v, referencing... Figure 4 The mapping data shown in (c) is used to set the steering current I according to the PID feedback control rule. S The proportional term gain K used in the decision P Differential term gain K D On the other hand, in the case of autonomous driving, in S15, the proportional term gain K P Differential term gain K D They were each set to low gain K PL Low gain K DL .

[0106] In the next step S16, the actual steering amount θ is detected by the steering amount sensor 80. In S17, the actual steering amount θ is determined relative to the target steering amount θ that has undergone filtering. *The deviation is the steering deviation Δθ, and based on this steering deviation Δθ and the set proportional term gain K P Differential term gain K D Integral term gain K I The steering current I to be supplied to the steering motor 24 is determined using the method described above according to the PID feedback control rule. S Then, in S18, the steering current I is supplied. S And the execution of this steering control program ends.

[0107] [2] Active stabilization system (second embodiment)

[0108] The active stability system (hereinafter, sometimes simply referred to as the "stability system") of the second embodiment as a vehicle behavior control system will now be described. It should be noted that this stability system is mounted on a vehicle 10 equipped with the aforementioned steering system.

[0109] (a) Composition of an active stable system

[0110] like Figure 8 As shown, this stability system is configured to include two stability devices 114 respectively disposed on the front wheel side and the rear wheel side of the vehicle 10. Each stability device 114 includes a stabilizer bar 120, which is connected at both ends to each of the lower suspension arms (not shown) of the wheel retaining members serving as wheel retaining members for each of the left and right wheels 12 via connecting rods 118. Figure 9 (Refer to). The stabilizer bar 120 is configured to include a pair of stabilizer bar members, namely a right stabilizer bar member 122 and a left stabilizer bar member 124, which are divided therein. The pair of stabilizer bar members 122 and 124 are connected via actuators 130, which are electric actuators, and are rotatable relative to each other. Generally speaking, the stabilizing device 114 causes the left and right stabilizer bar members 122 and 124 to rotate relative to each other by the actuators 130, thereby changing the apparent stiffness of the stabilizer bar 120 as a whole (hereinafter, sometimes referred to as "stabilizer stiffness") to suppress body roll. It should be noted that the stabilization system has some differences in the configuration of the stabilization device 114 on the front wheel side and the stabilization device 114 on the rear wheel side. Therefore, in the following description, when it is particularly necessary to distinguish between the front wheel side and the rear wheel side, the reference numeral for the front wheel side will be added with f, and the reference numeral for the rear wheel side will be added with r. Furthermore, when distinguishing between left and right, the reference numerals will be added with fr, fl, rr, and rl (meaning right front wheel side, left front wheel side, right rear wheel side, and left rear wheel side, respectively).

[0111] like Figure 9As shown in (a), the stabilizer bar members 122f and 124f of the front wheel side stabilizer 114f can be respectively divided into torsion bar portions 160fr and 160fl extending generally in the vehicle width direction, and arm portions 162 that are integrated with and intersect with each torsion bar portion 160fr and 160fl, extending generally towards the rear of the vehicle. The torsion bar portion 160fr of the right stabilizer bar member 122f is formed to be shorter, and the torsion bar portion 160fl of the left stabilizer bar member 124f is formed to be longer. The left stabilizer bar member 124f is further configured such that the torsion bar portion 160fl has the shape of a displacement portion 163, which is a portion bent in a state of displacement from the axis. On the other hand, in the rear wheel side stabilizer 114r, as Figure 9 As shown in (b), a pair of stabilizer bar members 122r and 124r can be divided into torsion bar portions 160rr and 160rl that extend to approximately the same length in the general vehicle width direction, and an arm portion 162 that is integrated with and intersects each torsion bar portion 160rr and 160rl and extends generally forward of the vehicle. Unlike the front wheel side stabilizer 114f, the torsion bar portions 160rr and 160rl are both straight, and the lengths between the actuator 130 and the arm portion 162 are set to be approximately equal to each other.

[0112] Each stabilizer bar component 122f, 122r, 124f, and 124r has a torsion bar portion 160 that is fixedly mounted on a support portion 164 of the vehicle body near the arm portion 162 and is rotatable, and is configured to be coaxial with each other. The front wheel side stabilizer 114f and the rear wheel side stabilizer 114r are each equipped with the aforementioned actuator 130 in a manner that connects the left and right torsion bar portions 160. Although this will be described in detail later, the end of each torsion bar portion 160 (the end on the side opposite to the arm portion 162) is connected to the actuator 130. Based on this configuration, the front wheel side stabilizer 114f is configured such that the actuator 130 is positioned after shifting from the center to the right in the vehicle width direction, and the rear wheel side stabilizer 114r is configured such that the actuator 130 is positioned approximately at the center in the vehicle width direction. On the other hand, the ends of each arm 162 (the ends on the side opposite to the torsion bar 160) are connected to the wheel retaining member via a connecting rod 118. It should be noted that the front wheel side stabilizer 114f is configured such that the limiting member 166 fixedly provided on the torsion bar 160fl and the actuator 130 abut against the mutually facing sides of the two support portions 164, thereby limiting positional changes in the vehicle width direction. The rear wheel side stabilizer 114r is configured such that each of the limiting members 166 fixedly provided on the torsion bar 160rr and 160rl abuts against the mutually facing sides of the two support portions 164, thereby limiting positional changes in the vehicle width direction.

[0113] Regarding the actuator 130, the same structure is used in the stabilizing devices 114 on both the front and rear wheel sides, such as... Figure 10 As schematically shown, the configuration includes an electric motor 170 as a drive source and a reducer 172 for reducing the rotation of the electric motor 170. The electric motor 170 and the reducer 172 are housed within a housing 174, which serves as the housing member of the actuator 130. As shown in the figure, a left balance bar member 124 is fixedly connected to the end of the housing 174. Furthermore, a right balance bar member 122 is disposed extending into the housing 174 and is supported so that it can rotate relative to the housing 174 but cannot move axially. The end of the right balance bar member 122 within the housing 174 is connected to the reducer 172.

[0114] The electric motor 170 is configured to include: a plurality of stator coils 184 fixedly arranged on a 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 a circumference on the outer periphery of the motor shaft 186, facing the stator coils 184. The electric motor 170 is a three-phase DC brushless motor in which the stator coils 184 function as the stator and the permanent magnet 188 functions as the rotor.

[0115] The reducer 172 includes a wave generator 190, a flexible gear 192, and a gear ring 194, and is configured to include a harmonic gear mechanism. The wave generator 190 is configured to include an elliptical cam and a ball bearing embedded in the outer periphery of the cam, and is fixed to one end of the motor shaft 186. The flexible gear 192 is configured with a cup-shaped peripheral wall that is elastically deformable, and a plurality of teeth are formed on the outer periphery of the open side of the peripheral wall. The flexible gear 192 is connected to and supported by the right balance bar member 122 described above. In detail, the right balance bar member 122 passes through the motor shaft 186, and at its end extending from the motor shaft 186, it is connected to the bottom serration of the flexible gear 192, which serves as the output of the reducer 172, so that it cannot rotate relative to the gear and cannot move relative to it axially. The gear ring 194 is generally annular, with a number of teeth (slightly more than the number of teeth on 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 embedded in the wave generator 190 and elastically deformed into an elliptical shape. The flexible gear 192 is configured to mesh with the gear ring 194 at two locations along the major axis of the ellipse, and not mesh at other locations. When the wave generator 190 rotates one revolution (360 degrees), that is, when the motor shaft 186 of the electric motor 170 rotates one revolution, the flexible gear 192 and the gear ring 194 rotate relative to each other by the difference in the number of teeth.

[0116] Based on the above configuration, when the vehicle 10 turns, a force—a roll moment—acts on the vehicle body causing a relative change in the distance between one of the left and right wheels 12 and the vehicle body, and the other of the left and right wheels 12 and the vehicle body. This causes the left and right balance bar members 122 and 124 to rotate relative to each other; that is, it exerts an external force on the actuator 130. In this case, when the actuator 130 exerts a force that balances its external force as an actuator force through the motor force generated by the electric motor 170 (the electric motor 170 is a rotary motor, so it can be considered as rotational torque, and is therefore sometimes called rotational torque), the balance bar 120 formed by the two balance bar members 122 and 124 is torn. The elastic force generated by this torsion becomes a force that counteracts the roll moment, that is, a roll suppression force. Furthermore, if the rotational position (i.e., the operating position) of the actuator 130 is changed by the motor force, thereby changing the relative rotational position of the left and right balance bar members 122 and 124, the aforementioned roll suppression force will change, thus enabling a change in the amount of body roll. This stabilization device 114 is configured to change the stiffness of the stabilizer in this way.

[0117] It should be noted that, within the actuator 130, a motor rotation angle sensor 196 is provided inside the housing 174 to detect the rotation angle ψ of the motor shaft 186, i.e., the rotation angle of the electric motor 170. In this actuator 130, the motor rotation angle sensor 196 is primarily an encoder. The motor rotation angle ψ serves as an indicator of the relative rotation angle (relative rotation position) of the left and right balance bar members 122 and 124. In other words, it is an indicator of the amount of motion, i.e., the amount of rotation, of the actuator 130, and is used for the control of the actuator 130, that is, the control of the stabilizing device 114.

[0118] like Figure 8 As shown, power is supplied from battery 66 to the electric motor 170 of actuator 130. In this stabilization system, a converter 64 is provided to boost the supply voltage generated by battery 66, and the power supply is configured to include the converter 64 and battery 66. A stabilizer electronic control unit (hereinafter, sometimes simply referred to as "stabilizer ECU") 140 is provided between the converter 64 and the two stabilization devices 114. Although not shown in the figure, the stabilizer ECU 140 is configured to include two converters that serve as drive circuits for the electric motors 170, and a computer, including a CPU, ROM, RAM, etc., which functions as a controller to control actuator 130. Power is supplied to the electric motors 170 of each of the two stabilization devices 114 via the converters in the stabilizer ECU 140. It should be noted that the electric motors 170 are driven by a constant voltage, therefore the supplied electrical energy is varied by changing the supply current, and the electric motors 170 exert a force corresponding to that supply current. In addition, the change in the supplied current is achieved by the converter changing the ratio (duty cycle) of the pulse-on time to the pulse-off time based on PWM (Pulse Width Modulation).

[0119] If reference Figure 8 To explain, in the stabilizer ECU 140, together with the aforementioned motor rotation angle sensor 196, there is an operation amount sensor 92 for detecting the operation amount (operation angle) δ of the steering wheel 16, which is a steering operation component, and for detecting the actual lateral acceleration Gy generated in the vehicle body. R The lateral acceleration sensor 198 is also connected to the stabilizer ECU 140 and is located on each of the four wheels 12 for detecting the speed v of each wheel. W The wheel speed sensor 94, the computer of the stabilizer ECU 140 is set to detect the vehicle speed v based on the detection value of the wheel speed sensor 94.

[0120] (b) Control of active stabilization systems

[0121] As described above, this stabilization system includes two stabilizing devices 114 on the front and rear wheels, and the stabilizer ECU 140, acting as the controller, independently controls each of the two stabilizing devices 114 according to a set roll stiffness distribution. As mentioned above, the two stabilizing devices 114 have substantially the same construction, and the control of each stabilizing device 114 is also substantially the same. In view of this, in the following description, the control of one stabilizing device 114 will be described for both the front and rear wheels.

[0122] i) Basic control

[0123] The stabilizer ECU 140 determines the target rotational position of the actuator 130 based on a roll moment index indicating the roll moment acting on the vehicle body, and controls the actuator 130 in such a way that the rotational position of the actuator 130 becomes the target rotational position. It should be noted that the rotational position of the actuator 130 referred to here means the amount of actuation of the actuator 130. Taking a state where the roll moment is completely absent from the vehicle body as a baseline state, and the rotational position of the actuator 130 in this baseline state as the neutral position, it means the amount of rotation from that neutral position. In other words, it means the displacement of the actuator 130's actuation position relative to the neutral position. Furthermore, the rotational position of the actuator 130 corresponds to the motor rotation angle, which is the rotation angle of the electric motor 170. Therefore, in actual control, the motor rotation angle ψ is used instead of the rotational position of the actuator 130. Furthermore, the actuator 130 is used to change the posture of the vehicle 10. More specifically, it is an electric actuator used to change the roll posture of the vehicle body. The stabilizer ECU 140, as a controller, controls the actuator 130 with the motor rotation angle ψ of the electric motor 170 as the controlled object.

[0124] To further explain the control of the stability device 114 in more detail, the lateral acceleration Gy, which is the aforementioned roll moment index, is a factor causing the attitude change of the vehicle 10. Based on this lateral acceleration Gy, the stabilizer ECU 140 determines the target motor rotation angle ψ, which is the target value of the motor rotation angle ψ, in order to obtain appropriate stabilizer stiffness. * In detail, the stabilizer ECU 140 bases its operation on the steering wheel 16 input δ detected by the input sensor 92 and the wheel speed v of each wheel 12 detected by the wheel speed sensor 94. W The estimated vehicle speed v is used to estimate the lateral acceleration Gy (hereinafter referred to as "estimated lateral acceleration Gy"). E "), and based on this presumed lateral acceleration Gy E And the actual lateral acceleration Gy detected by the lateral acceleration sensor 198R The control lateral acceleration Gy is determined according to the following formula. * .

[0125] Gy * =K E ·Gy E +K R ·Gy R

[0126] Among them, K E K R Weighting coefficient

[0127] The stabilizer ECU140 controls the lateral acceleration Gy based on the determined value. * To determine the target motor rotation angle ψ * Specifically, to achieve control of the lateral acceleration Gy * The appropriate stabilizer stiffness determines the target motor rotation angle ψ. * On the other hand, the stabilizer ECU 140 detects the actual motor rotation angle ψ as the actual value of the motor rotation angle ψ using the rotation angle sensor 196. The stabilizer ECU 140 bases this on the actual motor rotation angle ψ relative to the target motor rotation angle ψ. * The deviation of the motor rotation angle Δψ is used to determine the supply current I to the electric motor 170 according to the PID feedback control method. S Specifically, the supply current I is determined according to the same formula used in the steering system. S .

[0128] I S =K P ·Δψ+K D ·dΔψ / dt+K I ·∫Δψdt

[0129] Then, the stabilizer ECU140 determines the supply current I based on the above description. S The current is supplied to the electric motor 170 via a converter.

[0130] ii) Current reduction processing

[0131] In this stabilization system, considering energy saving and power reduction, the supply current to the actuator 130 is reduced under certain conditions. The following is an explanation of the current reduction process in this stabilization system.

[0132] In this stability system, similar to the steering system described above, considering the responsiveness of the actuator 130, the stabilizer ECU 140 is set to take the vehicle speed v of the vehicle 10 as the threshold vehicle speed v. THWhen the speed is below 20km / h to 30km / h, or when the vehicle 10 is in an automated driving mode, it is identified as a specific situation and the current is reduced.

[0133] In this stabilization system, unlike the steering system described above, as a current reduction process, only the supply current I is adjusted according to the feedback control method. S In the decision to reduce the gain K of the proportional term P Differential term gain K D The gain is reduced without performing low-pass filtering on the target actuator action. However, in this stable system, the gain K of the proportional term is reduced. P Differential term gain K D Set high gain K respectively PH High gain K DH and low gain K PL Low gain K DL The stabilizer ECU140 only converts the proportional gain K. P Differential term gain K D In non-specific situations, each is set to high gain K. PH High gain K DH In specific situations, K is set to low gain. PL Low gain K DL In other words, unlike the steering system described above, the proportional term gain K is not adjusted. P Differential term gain K D Based on the vehicle speed v, in high gain K PH High gain K DH With low gain K PL Low gain K DL The transition is gradual. The current reduction process described above also allows for significant energy savings and power efficiency improvements in this stable system.

[0134] In this stabilization system, the rotation angle of the electric motor 170 is the controlled object. Although detailed descriptions are omitted, in this stabilization system, as a current reduction process, the target motor rotation angle ψ, which is the target value of this controlled object, can also be considered. * The same low-pass filtering process as that in the steering system described above is performed. Furthermore, in the gain reduction process described above, the proportional term gain K can be reduced in the same way as in the gain reduction process in the steering system described above. P Differential term gain K D Based on the vehicle speed v, in high gain K PH High gain K DH With low gain K PL Low gain K DL The transition is gradual.

[0135] In the above-described steering system, the function of the steering ECU20, which acts as the controller, has been explained using a block diagram. However, the function of the stabilizer ECU140, which acts as the controller of this stability system, is the same, so the explanation using the block diagram is omitted.

[0136] iii) Control process

[0137] The control of the stabilizing device 114, as described above, is repeatedly executed by the computer of the stabilizer ECU 140 at short time intervals (e.g., a few milliseconds to tens of milliseconds). Figure 11 The stability control procedure is represented by a flowchart. The following is a brief explanation of the process according to the stability control procedure, referring to the flowchart.

[0138] In the process of the stability control procedure, firstly, in S21, the wheel speed v of each wheel 12 detected by the wheel speed sensor 94 is... W To estimate the vehicle speed v of the vehicle 10, in S22, the steering wheel operation amount δ is detected by the operation amount sensor 92. In S23, the lateral acceleration Gy is estimated based on the vehicle speed v and the operation amount δ. E An estimate is made. In subsequent S24, the actual lateral acceleration Gy is detected by the lateral acceleration sensor 198. R In S25, based on the estimated lateral acceleration Gy E And actual lateral acceleration Gy R As described above, the lateral acceleration Gy is determined. * .

[0139] In the following S26, based on the determined control lateral acceleration Gy * To determine the target motor rotation angle ψ * In S27, the actual motor rotation angle ψ is detected by rotation angle sensor 196.

[0140] In S28, it is determined whether the vehicle 10 is being driven autonomously. If it is being driven manually, in S29, it is determined whether the vehicle speed v is the threshold speed v. TH The following is an analysis of the determination that the vehicle speed v exceeds the threshold speed v. TH In the case of S30, the proportional term gain K is... P Differential term gain K D Set to high gain K respectively PH High gain K DH On the other hand, in the case of automated driving and in S29, the vehicle speed v is determined to be the threshold vehicle speed v. TH In the following cases, in S31, the proportional term gain K is... P Differential term gain K DSet to low gain K respectively PL Low gain K DL .

[0141] Then, in S32, the actual motor rotation angle ψ relative to the target motor rotation angle ψ is determined. * The deviation is the motor rotation angle deviation Δψ, and based on this motor rotation angle deviation Δψ and the set proportional term gain K P Differential term gain K D Integral term gain K I The supply current I to the electric motor 170 of the actuator 130 is determined by the method described above according to the PID feedback control rule. S In S33, the supply current I is supplied via a converter. S And the execution of this stability control procedure ends.

[0142] [3] Active suspension system (third embodiment)

[0143] The active suspension system (hereinafter, sometimes simply referred to as the "suspension system") of the vehicle behavior control system as a third embodiment will be described below. It should be noted that this suspension system is mounted on a vehicle 10 equipped with the aforementioned steering system and stability system.

[0144] (a) Composition of the active suspension system

[0145] like Figure 12 As shown, the suspension system of the third embodiment is configured to include: four suspension devices 220, corresponding to the four wheels 12 at the front, rear, left, and right; and a control system responsible for controlling these suspension devices 220. The suspension devices 220 of the front wheels (which act as steering wheels) and the suspension devices 220 of the rear wheels (which do not act as steering wheels) are considered to have substantially the same configuration except for the mechanism that enables steering of the wheels 12. Therefore, the description of the configuration of the suspension devices 220 will focus on the rear wheel suspension devices 220.

[0146] i) Composition of the suspension system

[0147] like Figure 13As shown, the suspension device 220 is an independent suspension device, configured as 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, which serve as suspension arms respectively. 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 holds the wheel 12 in a rotatable position. Through these five arms 230, 232, 234, 236, and 238, the axle carrier 240 is allowed to move up and down relative to the vehicle body along a fixed trajectory.

[0148] The suspension system 220 includes: two compression coil springs 246 and 248 arranged in series; an electromagnetic actuator (hereinafter, sometimes simply referred to as "actuator") 250 as an electric actuator; and a hydraulic damper 252. The two coil springs 246 and 248 cooperate to function as suspension springs that elastically connect the upper and lower parts of the spring. Furthermore, the actuator 250, which functions as a shock absorber, is disposed between a mounting portion 254, which is a component of the upper part of the spring and located on the tire housing, and a second lower arm 236, which is a component of the lower part of the spring.

[0149] ii) Composition of electromagnetic actuators

[0150] like Figure 14 As shown, the actuators 250 of each suspension device 220 are configured to include: an outer tube 260; and an inner tube 262, which is embedded in the outer tube 260 and protrudes upward from the upper end of the outer tube 260. Although described in detail later, the outer tube 260 is connected to the second lower arm 236 via a connecting mechanism 264 having a compression coil spring 248 as a component, and the inner tube 262 is connected to the mounting portion 254 at its upper end.

[0151] In the outer tube 260, a pair of guide grooves 266 extending axially into the actuator 250 are provided on its inner surface. Conversely, in the inner tube 262, a pair of keys 268 are attached to its lower end. These keys 268 are respectively embedded in the guide grooves 266, thereby enabling the outer tube 260 and inner tube 262 to be axially movable while remaining relatively non-rotatable. Furthermore, a dustproof seal 270 is provided at the upper end of the outer tube 260 to prevent the intrusion of external dust, mud, etc.

[0152] In addition, the actuator 250 includes: a hollow screw 272 with external threads; a nut 274 that retains bearing balls and engages with the screw 272; and an electric motor 276.

[0153] An electric motor 276 is fixed and housed within a motor housing 278, the flange of which is fixed to the upper surface of a mounting portion 254, thereby being fixed relative to the mounting portion 254. It should be noted that the upper end of an inner tube 262, which is formed in the shape of a flange, is also fixed to the flange of the motor housing 278. Through this construction, the inner tube 262 is fixedly connected to the mounting portion 254.

[0154] The motor shaft 280, which serves as the rotating shaft of the electric motor 276, is a hollow shaft and is integrally connected to the upper end of the screw 272. That is, the screw 272 is disposed within the inner tube 262 in a state that extends the motor shaft 280, and is given rotational force by the electric motor 276. On the other hand, the support cylinder 282 is fixed to the bottom of the outer tube 260 in a state that accommodates the screw 272 internally, and the nut 274 is fixed to the upper end of the support cylinder 282. The screw 272 and the nut 274, which are fixed to the support cylinder 282, are screwed together, forming a threaded mechanism 284.

[0155] According to the above-described structure, the actuator 250 is configured to include: an upper-sprung unit 286, which is configured to include an inner tube 262, a motor housing 278, an electric motor 276, a screw 272, etc.; and an unsprung unit 288, which is configured to include an outer tube 260, a support cylinder 282, a nut 274, etc. The actuator 250 is configured such that, with the relative movement of the upper and unsprung portions, the upper-sprung unit 286 and the unsprung unit 288 move relative to each other, thereby rotating the screw 272 and the electric motor 276. Furthermore, the actuator 250 generates an actuator force as a force against the relative movement of the upper-sprung unit 286 and the unsprung unit 288 by applying rotational force to the screw 272 via the electric motor 276. This actuator force acts on the upper and unsprung portions via a compression coil spring 248.

[0156] iii) Damper configuration

[0157] Each suspension device 220 includes a damper 252 configured as a cylinder device, disposed between the actuator 250 and the second lower arm 236. The damper 252 has a generally cylindrical housing 290. This housing 290 is connected to the second lower arm 236 at a connecting portion 292 fixedly provided at its lower end, and contains working fluid inside. A piston 294 is disposed inside the housing 290, which divides the interior of the housing 290 into an upper fluid chamber 296 and a lower fluid chamber 298, which are two fluid chambers, and is configured to slide relative to the housing 290.

[0158] Furthermore, the damper 252 has a piston rod 300, which is connected to the piston 294 at its lower end and extends from the cover of the housing 290. The piston rod 300 passes through a hole provided at the bottom of the outer tube 260, and also passes through the screw 272 and the motor shaft 280, and is fixed to the motor housing 278 at its upper end.

[0159] Damper 252 has a construction similar to a twin-tube shock absorber. (Refer to...) Figure 15 To elaborate further, the housing 290 is configured with a dual structure consisting of an outer cylinder 302 and an inner cylinder 304, with a buffer chamber 306 formed between the outer cylinder 302 and the inner cylinder 304. Furthermore, a partition wall 308 is provided near the bottom within the housing 290, and an auxiliary liquid chamber 312 is formed that communicates with the buffer chamber 306 via a connecting hole 310. That is, the lower liquid chamber 298 and the buffer chamber 306 are connected via the auxiliary liquid chamber 312.

[0160] The piston 294 is provided with multiple connecting passages 314, 316 that axially penetrate the piston 294 and connect the upper liquid chamber 296 and the lower liquid chamber 298. Figure 15 (Two are shown in the figure). In addition, in piston 294, there are circular plate-shaped valve members 318 and 320 made of elastic material on its lower and upper surfaces, respectively. The valve member 318 blocks the opening on the lower liquid chamber 298 side of the connecting passage 314, and the valve member 320 blocks the opening on the upper liquid chamber 296 side of the connecting passage 316.

[0161] Furthermore, similar to piston 294, partition wall 308 is provided with multiple connecting passages 322, 324 that connect lower liquid chamber 298 to auxiliary liquid chamber 312. Figure 15 (Two are shown in the figure). In addition, in the partition wall 308, there are circular plate-shaped valve members 326 and 328 made of elastic material on its lower and upper surfaces, respectively. The valve member 326 blocks the opening on the auxiliary liquid chamber 312 side of the connecting passage 322, and the valve member 328 blocks the opening on the lower liquid chamber 298 side of the connecting passage 324.

[0162] For example, when the piston 294 moves upward within the housing 290, a portion of the working fluid in the upper chamber 296 flows to the lower chamber 298 through the connecting passage 314, and a portion of the working fluid in the buffer chamber 306 flows into the lower chamber 298 through the connecting passage 324. At this time, the working fluid causes the valve members 318 and 328 to flex and flow into the lower chamber 298, thereby creating resistance to the upward movement of the piston 294. On the other hand, when the piston 294 moves downward within the housing 290, a portion of the working fluid in the lower chamber 298 flows to the upper chamber 296 through the connecting passage 316 and flows out to the buffer chamber 306 through the connecting passage 322. At this time, the working fluid causes the valve members 320 and 326 to flex and flow out from the lower chamber 298, thereby creating resistance to the downward movement of the piston 294.

[0163] According to the above-described configuration, the damper 252 is equipped with a flow resistance imparting mechanism. This mechanism, along with the up-and-down movement of the piston 294 relative to the housing 290, allows the flow of working 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, and imparts resistance to this flow. In other words, the damper 252 is configured to generate resistance to the relative movement of the upper and lower parts of the spring, i.e., to generate a damping force against this relative movement.

[0164] iv) Composition of suspension springs and connecting mechanisms

[0165] On the outer periphery of the housing 290, a lower spring seat 340 is attached in a flange shape. On the other hand, on the outer periphery of the outer tube 260, a middle spring seat 342 is attached in a flange shape. The compression coil spring 248 is configured in a compressed state, sandwiched between the lower spring seat 340 and the middle spring seat 342. Furthermore, the upper spring seat 346 is attached to the lower surface of the mounting portion 254 via anti-vibration rubber 344. The compression coil spring 246 is configured in a compressed state, sandwiched between the middle spring seat 342 and the upper spring seat 346.

[0166] With this configuration, the compression coil spring 246 functions as a connecting spring that elastically connects the upper and lower spring side units 288, and the compression coil spring 248 functions as a support spring that elastically supports the lower spring side unit 288 to the lower spring. Therefore, the compression coil spring 246 and the compression coil spring 248 cooperate with each other to function as suspension springs that elastically connect the upper and lower spring parts. Furthermore, the compression coil spring 248 is incorporated into the connecting mechanism 264 that elastically connects the lower spring part and the lower spring side unit 288.

[0167] In other words, in this suspension device 220, the upper spring side unit 286 of the actuator 250 is fixedly connected to the upper spring portion, which serves as the unit's fixed portion, as a fixed unit. On the other hand, the lower spring side unit 288 is floatingly supported on the lower spring portion, which serves as the unit's floating support portion, as a floating unit. In addition, in this suspension device 220, the lower spring side unit 288 is also floatingly supported on the upper spring portion by a compression coil spring 246.

[0168] The connecting mechanism 264 is configured to allow relative movement between the unsprung side unit 288 and the unsprung portion, but the relative displacement between the unsprung side unit 288 and the unsprung portion during this relative movement is limited by the relative displacement limiting mechanism 350 of the connecting mechanism 264. The relative displacement limiting mechanism 350 is composed of the bottom of the outer tube 260, the upper end of the housing 290 of the damper 252, a cylindrical skirt 352 attached to the bottom of the outer tube 260, and a locking ring 354 attached to the outer periphery of the housing 290.

[0169] Specifically, when the unsprung side unit 288 is close to the unsprung portion, the approach is limited by the bottom of the outer tube 260 abutting against the upper end of the housing 290 of the damper 252 via the cushioning rubber 356. On the other hand, when the unsprung side unit 288 is separated from the unsprung portion, the separation is limited by the lower end of the skirt 352, which is formed as an inner flange, abutting against the locking ring 354 via the cushioning rubber 358.

[0170] v) The composition of the control system

[0171] In the suspension system of this embodiment, such as Figure 12 As shown, specifically, a suspension electronic control unit 370 (hereinafter sometimes abbreviated as "suspension ECU370") is provided as a controller for controlling the operation of the four actuators 250 with the actuator force of each actuator 250 as the control object. The suspension ECU370 is mainly composed of a computer equipped with CPU, ROM, RAM, etc., and includes four converters that serve as drive circuits for the electric motors 276 of each actuator 250. Each converter is connected to a battery 66, which serves as 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 by a constant voltage. The actuator force of each actuator 250 is controlled by controlling the current flowing to each electric motor 276. This current control is achieved by changing the ratio (duty cycle) of the pulse on-time to pulse off-time in PWM (Pulse Width Modulation). In addition, the rotation angle φ of each electric motor 276 is detected by the motor rotation angle sensor 378, and the converter controls the operation of each electric motor 276 based on the detected motor rotation angle φ.

[0172] In the suspension ECU 370, in addition to the four motor rotation angle sensors 378 mentioned above, there is also an operation amount sensor 92 for detecting the operation amount (operation angle) δ of the steering wheel 16, which is a steering operation component, and an actual lateral acceleration Gy, which is the actual lateral acceleration Gy generated in the vehicle body. R The system includes a lateral acceleration sensor 198 and a front and rear acceleration sensor 384 that detects the front and rear acceleration Gx generated on the vehicle body. Furthermore, various sensors corresponding to the four suspension units 220 are connected, specifically, sensors that detect the sprung acceleration Gx, which is the longitudinal acceleration of the sprung portion. U The sprung longitudinal acceleration sensor 386 detects the unsprung acceleration G, which is the longitudinal acceleration of the unsprung part. L The suspension ECU 370 includes an unsprung longitudinal acceleration sensor 388 and a travel sensor 390 for detecting the travel amount S, which is equivalent to the distance between the sprung and unsprung parts. The suspension ECU 370 is also connected to four wheel speed sensors 94, each corresponding to one of the four wheels and used to detect the rotational speed of its respective wheel. The suspension ECU 370 is configured to detect the vehicle speed v, which is the driving speed of the vehicle 10, based on the detection values ​​of these wheel speed sensors 94.

[0173] In the control system of this suspension system, the suspension ECU370 controls the current supplied to the electric motor 276 of each actuator 250 based on signals from the various sensors mentioned above, thereby controlling the operation of each actuator 250, that is, controlling the actuation force of each actuator 250.

[0174] (b) Control of electromagnetic actuators

[0175] In this suspension system, the suspension ECU 370 performs the following two controls by controlling the actuators 250 of each of the four suspension components 220. Specifically, it performs sprung vibration damping control to attenuate the vibration of the sprung parts, and vehicle attitude change suppression control to suppress vehicle pitch and roll. Given the significance of the vehicle attitude change suppression control, the actuator 250 can be considered as an electric actuator for changing the vehicle's attitude. The four actuators 250 have substantially the same construction and function, and their control can be considered identical. Therefore, the control of one actuator 250 for each suspension component 220 will be described below.

[0176] i) Vibration damping control of the upper part of the spring

[0177] The vibration model based on the actual device configuration of the aforementioned suspension device 220 (hereinafter, sometimes referred to as the "actual device model") becomes Figure 16The model shown in (a) is a vibration model that includes, in addition to, the sprung mass M, which is the inertial mass of the sprung portion. U and the unsprung mass M, which is the inertial mass of the unsprung part. L In addition, it also includes the intermediate mass M, which constitutes the inertial mass (described later) of the unsprung side unit 288 of the actuator 250. I The model. In this model, the mass M on the spring... U With unsprung mass M L A damper equivalent to damper 252 is provided between them, that is, a damper C1 with a damping coefficient of C1. Furthermore, the spring mass M... U With intermediate mass M I A spring equivalent to a compression coil spring 246, i.e., a spring K1 with a spring constant of K1 and an actuator A equivalent to an actuator 250, are connected in parallel between them. Furthermore, in the intermediate mass M... I With unsprung mass M L A spring equivalent to a compression coil spring 248 is provided between them, that is, a spring K2 with a spring constant of K2. In addition, the unsprung mass M L A spring equivalent to a tire is installed between the spring and the road surface, that is, a spring K3 with a spring constant of K3.

[0178] On the other hand, the control model, which serves as the theoretical model for controlling the actuator 250, is, for example, Figure 16 The model shown in (b) has a spring mass M U Become through a damping coefficient of C S Sky Hook Damper C S The suspended model. That is to say, the control model is based on the theory of ceiling dampers.

[0179] In the vibration damping control of the upper part of the spring, according to the configuration of the ceiling damper C S The above control model uses the actuator force generated by actuator A in the actual device model as a reference to the ceiling damper C in the control model. S The resulting damping force controls the actuator 250 in a manner equivalent to a force. More specifically, it is based on the longitudinal acceleration G of the spring detected by the spring longitudinal acceleration sensor 386. U (Hereinafter, sometimes referred to as "spring acceleration G") U The spring velocity v, which is the absolute velocity of the spring, is calculated using this method. U And to generate an actuator force according to the following formula, that is, with the spring velocity v U The corresponding actuator force is used as the damping component F of the upper spring vibration. U The operation of the electric motor 276 is controlled in this way.

[0180] F U =C S ·v U

[0181] In addition, the damping coefficient C S This can be considered as the control gain and is set to a value suitable for effectively attenuating vibrations at and near the sprung resonant frequency. It should be noted that in this suspension system, damper 252 is used to address the unsprung resonance phenomenon. That is, the damping coefficient C1 of damper C1 in the above-mentioned actual device model and control model, i.e., the damping coefficient of damper 252, is set to a value suitable for effectively attenuating vibrations at and near the unsprung resonant frequency.

[0182] ii) Vehicle posture change suppression control

[0183] In this suspension system, in addition to sprung vibration damping control, vehicle attitude change suppression control is also implemented to mitigate body roll caused by vehicle cornering and body pitch caused by vehicle acceleration and deceleration. In this body attitude change suppression control, actuator 250 generates forces that counteract the roll moment acting on the vehicle body as a cause of body roll and forces that counteract the pitch moment acting on the vehicle body as a cause of body pitch.

[0184] More specifically, regarding the body roll, based on the aforementioned roll moment, the actuators 250 of each of the two suspension devices 220 on the inner wheel side of the turn generate an actuator force in the direction that brings the upper and lower parts of the spring closer together (hereinafter, sometimes referred to as the "bounce direction"). On the other hand, the actuators 250 of each of the two suspension devices 220 on the outer wheel side of the turn generate an actuator force in the direction that separates the upper and lower parts of the spring (hereinafter, sometimes referred to as the "rebound direction"), which serves as the roll suppression component F. R (It is a type of postural change inhibition component.)

[0185] Specifically, using the same method as in the aforementioned stabilization system, the estimated lateral acceleration Gy is estimated based on the steering wheel 16 operation amount δ and vehicle speed v. E and the actual lateral acceleration Gy detected by lateral acceleration sensor 198 R The control lateral acceleration Gy is determined according to the following formula. * .

[0186] Gy * =K E ·Gy E +K R ·Gy R

[0187] Among them, K E K R Weighting coefficient

[0188] The lateral acceleration Gy determined in this way is * It is a roll moment index that indicates the roll moment acting on the vehicle body, based on which the lateral acceleration Gy is controlled. * The roll suppression component F is determined according to the following formula. R .

[0189] F R =K Y ·Gy *

[0190] (K Y (tilt suppression gain)

[0191] Roll suppression component F R It is a component of the actuator force and is the controlled object of actuator 250. Furthermore, the lateral acceleration Gy is a factor causing changes in the attitude of vehicle 10. As described above, suspension ECU 370, based on the lateral acceleration Gy, which is a factor causing changes in the attitude of vehicle 10, adjusts the roll suppression component F... R The target value is determined for the controlled object.

[0192] Regarding vehicle pitch, specifically, for the nose-dive that occurs during vehicle braking, the actuators 250 of the two suspension devices 220 on the front wheels generate a rebound force based on the pitch moment. On the other hand, the actuators 250 of the two suspension devices 220 on the rear wheels generate a bounce force, which are respectively used as pitch suppression components F. P Furthermore, in response to the body squat that occurs during vehicle acceleration, the actuators 250 of the two rear-wheel suspension devices 220 generate a rebound force based on the pitch moment. On the other hand, the actuators 250 of the two front-wheel suspension devices 220 generate a bounce force, which are respectively used as pitch suppression components F. P (It is a type of postural change inhibition component.)

[0193] Specifically, the pitch moment index, which indicates the pitch moment, is the actual forward and backward acceleration Gx detected by the forward and backward acceleration sensor 384. Based on this actual forward and backward acceleration Gx, the pitch suppression component F is determined according to the following formula. P .

[0194] F P =K X ·Gx

[0195] (K X (Pitch suppression gain)

[0196] Pitch suppression component F P It is also a component of the actuator force and is controlled by actuator 250. Furthermore, the front-to-rear acceleration Gx is also a factor causing changes in the attitude of vehicle 10. As described above, suspension ECU 370, based on the front-to-rear acceleration Gx, which is a factor causing changes in the attitude of vehicle 10, controls the pitch suppression component F... P The target value is determined for the controlled object.

[0197] iii) Integration of two controls

[0198] The aforementioned sprung vibration damping control and vehicle body posture change suppression control are performed comprehensively, and the sprung vibration damping component F in these controls... U , roll suppression component F R Pitch suppression component F P They are processed uniformly. Specifically, these components F U F R F P The combined actuator force F that actuator 250 should generate is determined by summing up the following formula.

[0199] F = F U +F R +F P

[0200] Each component F U F R F P The combined actuator force F is the actuator force that each of the four suspension devices 220's actuators 250 should generate. To generate this actuator force, the operation of the electric motor 276 of each actuator 250 is controlled. Specifically, the generated actuator force F is approximately proportional to the current supplied to the electric motor 276 of each actuator 250. The suspension ECU 370 determines the supply current I, which is the current that should be supplied to the electric motor 276 of each actuator 250, based on the actuator force F that each actuator 250 should generate. S And based on the supply current I S Current is supplied to the electric motor 276 via a converter.

[0201] iv) Current reduction processing

[0202] In this suspension system, considering energy conservation and power saving, current reduction processing is also performed on the current supplied to the actuator 250, i.e., the current supplied to the electric motor 276, under certain conditions. The current reduction processing in this suspension system will be explained below.

[0203] In this suspension system, similar to the steering and stability systems described above, considering the responsiveness of the actuator 250, the suspension ECU 370 is set to take the vehicle speed v of the vehicle 10 as the threshold vehicle speed v. TH When the speed is below 20km / h to 30km / h, or when the vehicle 10 is in autonomous driving mode, it is identified as a specific situation and current reduction processing is performed.

[0204] In this suspension system, the component targeted for current reduction processing is the aforementioned attitude change suppression component, specifically, only the roll suppression component F. R Pitch suppression component F P The vibration damping component F of the upper part of the spring mentioned above U It is not targeted for current reduction processing. Furthermore, unlike the steering system described above, it does not undergo the aforementioned gain reduction processing; instead, it performs low-pass filtering processing only on the target actuator action quantity. That is, it only applies to the roll suppression component F. R Pitch suppression component F P Low-pass filtering is implemented. However, this low-pass filtering is only implemented under specific conditions, and not under other conditions. Furthermore, a cutoff frequency f based on the driving mode is not performed. C The change does not involve adjusting the cutoff frequency f corresponding to the vehicle speed v. C The gradual change. That is to say, only under specific conditions, the roll suppression component F... R Pitch suppression component F P Implementation cutoff frequency f C Fixed to low frequency f CL1 Low-pass filtering is applied. This current reduction process also fully realizes the energy-saving and power-saving benefits of this suspension system.

[0205] It should be noted that, for example, similar to the steering system described above, the cutoff frequency f can be increased even outside of specific conditions. C Low-pass filtering is performed. Furthermore, similar to the steering system described above, the cutoff frequency f can be changed based on vehicle speed v and driving mode. C To perform low-pass filtering.

[0206] In the above-described steering system, the function of the steering ECU20, which acts as the controller, has been explained using a block diagram. However, the function of the suspension ECU370, which acts as the controller of this suspension system, can be easily deduced by analogy, so the explanation using the block diagram is omitted.

[0207] v) Control Process

[0208] The actuator 250, as described above, is controlled repeatedly by the computer of the suspension ECU 370 at short time intervals (e.g., a few milliseconds to tens of milliseconds). Figure 17 The suspension control procedure is represented by a flowchart. The following is a brief explanation of the processing flow according to the suspension control procedure, referring to the flowchart.

[0209] In the suspension control procedure, firstly, in S41, the sprung acceleration G is detected by the sprung longitudinal acceleration sensor 386. U In S42, based on the spring acceleration G U To calculate the spring velocity v U Next, in S43, based on this sprung velocity v U The damping coefficient C of the ceiling damper S To determine the vibration damping component F of the upper part of the spring U .

[0210] Next, in S44, it is decided to control the lateral acceleration Gy. * This controls the lateral acceleration Gy * The decision is made through the same process as S21 to S25 of the stability control procedure. Based on the determined control lateral acceleration Gy... * In S45, the roll suppression component F is determined. R In the subsequent S46, the forward and backward acceleration Gx is detected by the forward and backward acceleration sensor 384. In S47, the pitch suppression component F is determined based on the detected forward and backward acceleration Gx. P .

[0211] In S48, it is determined whether the vehicle 10 is being driven autonomously. If it is being driven manually, in S49, it is determined whether the vehicle speed v is the threshold speed v. TH The following applies: In S48, if the vehicle is determined to be in a state of automated driving, or in S49, if the vehicle speed v is determined to be the threshold speed v... TH In the following cases, in S50, the roll suppression component F R and pitch suppression component F P Implementation cutoff frequency f C Set to low frequency f CL1 Low-pass filtering processing.

[0212] Next, in S51, the vibration damping component F of the upper part of the spring is... U And the roll suppression component F with or without low-pass filtering R Pitch suppression component F PThe summation determines the combined actuator force F that should be generated. In S52, based on this actuator force F, the supply current I, which is the current that should be supplied to the electric motor 276 of the actuator 250, is determined. S Then, in S53, based on the supply current I... S Current is supplied to the electric motor 276 via the converter, and one execution of this suspension control program is completed.

Claims

1. A vehicle behavior control system comprising: an electric actuator mounted on a vehicle and used to change the posture of the vehicle; and a controller that controls the magnitude of the electric actuator's motion or the force generated by the electric actuator as the controlled object, wherein... The controller is configured to: The target value of the controlled object is determined based on at least one of the posture the vehicle should adopt and the factors that cause the change in the vehicle's posture, and current is supplied to the electric actuator based on this target value; and Under certain conditions, a current reduction process is performed to reduce the current supplied to the electric actuator. The controller is configured to: Current is supplied to the electric actuator through feedback control based on the deviation of the actual value of the controlled object from the target value; and As part of the current reduction process, under the specific condition, the gain in the feedback control is reduced compared to when the specific condition is not met. The vehicle is configured to operate in both manual and automatic modes by a driver. The specific state is defined when operating in automatic mode and when operating in manual mode and the vehicle's speed is below a set speed.

2. The vehicle behavior control system according to claim 1, wherein, The condition in which the operation of the electric actuator does not require high responsiveness is defined as the specific condition.

3. The vehicle behavior control system according to claim 1, wherein, The controller is configured, as part of the current reduction process, to further include: performing low-pass filtering on the target value only under the specific condition, or, under the specific condition, reducing the cutoff frequency in the low-pass filtering applied to the target value compared to when it is not the specific condition.

4. The vehicle behavior control system according to any one of claims 1 to 3, wherein, The electric actuator is a steering actuator used to turn the wheels. The vehicle behavior control system is the steering system.

5. The vehicle behavior control system according to any one of claims 1 to 3, wherein, The vehicle is equipped with a stabilizer bar, with its two ends connected to the left and right wheels respectively. The stabilizer bar is used to suppress body roll. The electric actuator is used to change the roll-damping force exerted by the stabilizer bar. The vehicle behavior control system is an active stability system.

6. The vehicle behavior control system according to any one of claims 1 to 3, wherein, The electric actuator is an actuator that exerts force on the relative movement of the wheels and the vehicle body in the vertical direction. The vehicle behavior control system is an active suspension system.

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