JP2008062699A - Controller for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the influence of a state of a power source load upon behavior of a vehicle. <P>SOLUTION: When a ratio of the lateral force Ff of front wheels to the lateral force Fr of rear wheels shows a possibility of applying yaw vibration to a vehicle 10, an ECU 100 controls an EPS 200 so that a convergent steering torque Tc for steering the front wheels in a direction to converge the yaw vibration is applied to the front wheels. Meanwhile, when a battery 24 to be a power source of the EPS 200 is in a heavy load state, if the vehicle 10 is braked, the ECU 100 determines a distribution of breaking force for each wheel so as to produce the similar effect as when the torque Tc is applied, and controls braking actuator 23. As a result, moment around a king pin shaft corresponding to each wheel varies in response to the distribution of the braking force, and the turning to a specific direction is facilitated or blocked. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technical field of a vehicle control device that controls the behavior of a vehicle at the time of steering, for example.

  In this type of technical field, there has been proposed one that detects a friction coefficient of a road surface for vehicle behavior control (see, for example, Patent Document 1). According to the road surface friction coefficient detection control device (hereinafter referred to as “prior art”) disclosed in Patent Document 1, the yaw moment generated in the vehicle is obtained from the magnitude of the driving force applied to the wheels, and the yaw moment By correcting the steering angle of the front wheels or rear wheels so as to cancel out the vehicle, it is possible to predict the occurrence of yawing at the time of detecting the road surface friction coefficient, and to suppress the decrease in the running stability of the vehicle. Yes.

  For such control of the steering angle, means for assisting the steering force by using electric power supplied from a power source such as EPS (Electronic Control Power Steering) can be used.

  A technique for controlling the yaw moment of the vehicle by distributing the braking force has also been proposed (see, for example, Patent Document 2).

  Also proposed is a technique for improving the turning response by correcting the yaw moment applied to the vehicle by the yaw moment due to the difference in braking force between the left and right wheels in a situation where the vehicle is applied with the yaw moment by steering the steered wheels. (For example, see Patent Document 3).

Japanese Patent Laying-Open No. 2005-306081 JP-A-8-268248 JP 2006-21589 A

  The use of a power supply device such as EPS as a power source may be restricted depending on the load state of the power supply. In this case, various steering controls including the control according to the related art as described above are executed. Becomes substantially difficult. That is, in the prior art, even if an attempt is made to stabilize the behavior of the vehicle by steering control via EPS or the like, the behavior of the vehicle cannot be sufficiently controlled depending on the load state of the power source, and the behavior of the vehicle is relatively There is a technical problem that can lead to instability.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a vehicle control device that can reduce the influence of the load state of the power supply on the behavior of the vehicle.

  In order to solve the above-described problems, a vehicle control device according to the present invention includes a power supply device, and a steering force application unit that is at least partially driven by electric power supplied from the power supply device and can apply a steering force to at least a front wheel. And a vehicle control device that controls a vehicle including a braking force applying means capable of applying a braking force to each of the front wheels and the rear wheels, and is associated with a behavior state of the vehicle during steering of the front wheels. A first specifying means for specifying a predetermined index value, and a stabilizing steering force for steering the front wheel in a direction to stabilize the behavior as at least a part of the steering force based on the specified index value. Steering control means for controlling the steering force application means, and at least a part of the deceleration period of the vehicle by a braking force applied to each of them instead of the stabilization steering force Serial behavior characterized by comprising a braking control means for controlling the braking force application means to be stable.

  The “power supply device” according to the present invention may be, for example, a vehicle-mounted 12V battery or the like that can function as a power supply device for various auxiliary devices provided in a vehicle such as a cell motor, cigar lighter, blower, headlight, or car navigation device. However, a dedicated battery or the like configured independently of such an auxiliary battery may be used. Furthermore, a battery capable of supplying a relatively high secondary voltage by appropriately boosting the voltage supplied from these various batteries may be used.

  The “steering force applying means” according to the present invention is driven at least in part by the electric power supplied from the power supply device, and at least the front wheel is operated by the driver depending on the situation depending on the steering operation by the driver. It is a concept encompassing means capable of applying a steering force according to the motion state of the vehicle at that time irrespective of the current state. As long as such a concept is secured, for example, the physical, mechanical, mechanical, or electrical configuration of the steering force applying means is not limited.

  The steering force applying means according to the present invention is a steering force (or steering torque) corresponding to an operation amount (for example, steering angle or steering torque) related to a steering operation by an operator via an operation means such as a steering wheel. ) Is mechanically transmitted to the target wheel, for example, appropriate control is performed by electric power supplied from the power supply device regardless of whether it is defined including, for example, various known steering devices such as a rack and pinion or a ball nut method. For example, it is intended to include at least a part of various assist means such as a motor that can be driven through control of the system, and preferably, at least a part of each of the steering device and the various assist means such as an EPS and an active steering device. Take a form in which they are configured integrally with each other.

  According to such a steering force applying means according to the present invention, for example, the steering torque generated in the steering shaft or the like when the driver operates the steering wheel, or the steering angle of the steering wheel when the driver operates the steering wheel, for example. Assist steering force that assists, for example, a steering force (steering torque) from, for example, a motor or the like according to the steering speed or the like, or according to the motion state of the vehicle at that time regardless of the steering operation by such a driver, for example. (Assist steering torque) is output, and a part of the operation of the steering device, for example, the rotational motion of the steering shaft, or the rack and pinion type steering device, for example, the reciprocating motion of the rack, the rotational motion of the pinion gear, etc. Assisted. Alternatively, the steering angle of the target wheel via the steering device is directly controlled by, for example, a steering torque output from a motor or the like according to the motion state of the vehicle, regardless of the driver's steering operation. As a result, the steering force including these assist torque and steering torque is transmitted to the target wheel.

  The vehicle according to the present invention is provided with braking force applying means in addition to such steering force applying means. The “braking force applying means” according to the present invention is a concept encompassing means capable of applying a braking force to each of the front wheels and the rear wheels. For example, an ECB (including an ABS (Antilock Braking System)) or the like. Electronic Controlled Braking system: etc.

  For example, the physical, mechanical, mechanical, or electrical configuration of the braking force applying means according to the present invention is not limited as long as the braking force can be individually applied to each of the front wheels and the rear wheels. In order to control each braking force, the hydraulic pressure of the brake fluid supplied to each wheel cylinder provided individually depends on each wheel speed, slip state, vehicle yaw rate, longitudinal acceleration, lateral acceleration, etc. For example, by changing the driving force of an electric pump, various electromagnetic control valves, etc., through a hydraulic control system such as a brake actuator, which is configured to be able to control each braking force individually. In addition, each of the braking forces may be individually controlled. In view of the fact that the braking force applying means according to the present invention can preferably take the form of ECB or the like, the braking force applying means is also a load of the power supply apparatus described above.

  According to the vehicle control device of the present invention, the first control unit can take various forms such as various processing units such as an ECU (Electronic Control Unit), various controllers, various computer systems such as a microcomputer device, and the like. The specifying means specifies a predetermined index value associated with the behavior state of the vehicle when the front wheels are steered.

  Here, the “predetermined index value associated with the behavior state of the vehicle when steering the front wheels” means, for example, the speed, yaw rate, longitudinal acceleration and lateral acceleration, longitudinal force applied to the wheels, lateral force and friction in the vehicle. Force, wheel speed, wheel slip ratio, wheel ground load, steering angle, steering speed, steering torque, etc. alone or in combination with other index values as appropriate, in advance when steering the front wheels, that is, turning (turning) It is a concept that includes index values that are defined as qualitatively or quantitatively representing the behavior of the vehicle at the time.

  Note that “specific” in the present invention refers to, for example, detecting directly or indirectly as a physical numerical value or an electrical signal or the like corresponding to a physical numerical value via some detection means, appropriate storage means, etc. Selecting a corresponding numerical value from a map or the like stored in the map, or estimating through such selection, a preset algorithm based on the detected physical numerical value or electrical signal or the selected or estimated numerical value It is a broad concept encompassing deriving according to the calculation formula or the like, or simply acquiring the value detected, selected, estimated or derived as such as an electric signal or the like.

  When the index value is specified, the steering control means that can take the form of various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device, based on the specified index value, at least the steering force. As a part, the steering force applying means is controlled so that a stabilized steering force for steering the front wheels in a direction in which the behavior of the vehicle is stabilized is applied.

  Here, the mode of stabilizing the behavior of the vehicle by applying the stabilizing steering force is made based on the index value specified by the first specifying means and is considerably more than that in the case where this kind of control is not performed. The purpose is not limited as long as the behavior of the vehicle can be stabilized, and for example, the steering angle is increased when the vehicle bulges outside the turn than the direction intended by the driver (ie, understeer occurs). Stabilizing steering force may be applied, or the steering angle may be decreased when the vehicle is cut inward of the turn than the direction intended by the driver (that is, oversteering occurs). A steering force may be applied. Alternatively, as one of the stabilizing steering forces, vibration in the yaw direction of the vehicle (hereinafter referred to as “yaw vibration” as appropriate), vibration of the front wheel as the steering wheel, or further vibration of the front wheel via the steering device. Convergence steering force, which will be described later, is applied to converge the coupling with the vibration of the steering wheel as transmitted to the steering wheel (hereinafter, the term “steering vibration” will be used as a general term). May be.

  Here, in particular, the application of the stabilized steering force by the control of the steering control means described above is different in nature from the application of the steering force for assisting the steering operation of the driver, for example, transient, continuous, and high load. Often. On the other hand, the power capacity of the power supply device is finite, and there are many cases where there is not enough room to withstand constant execution of the stabilizing steering force. In particular, as described above, this tendency is conspicuous when used in common with vehicle auxiliary machinery. For this reason, in this type of vehicle, depending on the load state of the power supply device, it may be difficult to control the behavior of the vehicle by applying a stabilizing steering force, and inevitably the behavior of the vehicle may become unstable. There is.

  Therefore, in the vehicle control device according to the present invention, the influence of the load state of the power source on the behavior of the vehicle is reduced as follows. That is, according to the vehicle control device of the present invention, during operation, the vehicle deceleration device is operated by the braking control means that can take the form of various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device. In at least part of the period, the braking force applying means is controlled so that the behavior of the vehicle during front wheel steering is stabilized by the braking force applied to each of the front wheels and the rear wheels instead of the stabilizing steering force.

  The mode in which the behavior control by applying the stabilizing steering force is replaced by the application of the braking force is compared with the case where this kind of alternative control is not performed (that is, the stabilization steering force is not simply applied). As long as the behavior of the vehicle is stabilized to a certain extent (for example, the braking force applied to one of the left and right front wheels or the braking force applied to one of the left and right rear wheels). May be relatively increased with respect to the other to suppress turning in a specific direction (or to promote turning in a specific direction).

  Here, during the deceleration period of the vehicle, a braking operation by the braking force applying means is originally performed through the control by the braking control means separately from this kind of behavior control. Therefore, when the braking force is used for vehicle behavior control, for example, by changing the braking force distribution between the wheels, the effect on the load state of the power supply device can be ignored at least newly stabilized. This is smaller than operating the steering force applying means to apply the steering force.

  Alternatively, depending on the configuration of each of the braking force applying means and the steering force applying means, the application of the braking force mainly performed by the opening / closing operation of various electromagnetic on / off valves such as the pressure reducing valve and the holding valve may be performed by applying the steering force. The power load may be smaller than when a part of the device is physically driven.

  Thus, according to the vehicle control apparatus of the present invention, the braking force applying means that is originally operating at least in a case where the condition for applying the stabilizing steering force during the deceleration period of the vehicle is satisfied. With the applied braking force, it is possible to obtain the same effect as when the stabilized steering force is applied. Accordingly, it is possible to stabilize the behavior of the vehicle without substantially affecting the load state of the power supply device, and to reduce the influence of the load state of the power supply device on the behavior of the vehicle. .

  In one aspect of the vehicle control apparatus according to the present invention, the first specifying means includes an index value corresponding to a lateral force acting on the front wheel and a lateral force acting on the rear wheel as at least part of the index value. The steering control means determines the stability when the ratio of the lateral force acting on the rear wheel to the lateral force acting on the front wheel is a ratio that causes yaw vibration in the vehicle. The steering force applying means is controlled so that a convergent steering force for steering the front wheels in a direction for converging the yaw vibration is applied as the normalized steering force.

  According to this aspect, the first specifying means acts on the index value corresponding to the lateral force acting on the front wheel (hereinafter referred to as “front wheel lateral force” as appropriate) and the rear wheel as at least a part of the index value described above. Index values corresponding to the lateral force to be applied (hereinafter referred to as “rear wheel lateral force” as appropriate) are specified. The ratio of the rear wheel lateral force to the front wheel lateral force can be an index that defines whether or not yaw vibration occurs in the vehicle.

  The yaw vibration and the steering vibration interact with each other. The yaw vibration promotes the generation of the steering vibration, and the steering vibration causes the generation of the yaw vibration. In particular, when the phase of the steering vibration and the phase of the yaw vibration are opposite to each other, that is, when the steering vibration and the yaw vibration are coupled to each other, the convergence of the yaw vibration (that is, the steering simultaneously) (Convergence of vibration) is slow, and the behavior of the vehicle in the yaw direction (that is, an example of the behavior of the vehicle during front wheel steering) tends to be unstable.

  According to this aspect, when the ratio is a ratio defined as causing the vehicle to yaw vibrate, the front wheel in a direction that converges the yaw vibration, such as a neutral steering direction, as the stabilizing steering force, for example. A converging steering force for steering is applied, and this converging steering force cancels the moment about the kingpin axis in the front wheels corresponding to the steering vibration. For this reason, it becomes possible to converge the yaw vibration of the vehicle efficiently and effectively, and it becomes possible to quickly converge the coupling of the yaw vibration and the steering vibration.

  In addition, “when the vehicle has a ratio defined as causing the vehicle to yaw vibrate” means that the ratio of the rear wheel lateral force to the front wheel lateral force does not necessarily have to be used as a criterion. When the correspondence relationship between the ratio of the rear wheel lateral force to the front wheel lateral force is known or can be estimated based on experience or simulation, as a criterion, for example, the rear wheel lateral force Various indexes based on index values corresponding to the front wheel lateral force and the rear wheel lateral force, such as the ratio of the front wheel lateral force to the front wheel or the ratio of the rear wheel lateral force to the front wheel steering angle, may be used.

  In this aspect, the steering control means is configured to apply the convergent steering force when the ratio of the lateral force acting on the rear wheel to the lateral force acting on the front wheel is equal to or greater than a predetermined value. The steering force applying means may be controlled.

  According to this aspect, since the convergence steering force is applied to the front wheels when the ratio of the rear wheel lateral force to the front wheel lateral force is equal to or greater than a predetermined value, the yaw vibration is generated. Such a determination can be made relatively easily. Also, yaw vibration tends to be more prominent as the rear wheel lateral force is greater than the front wheel lateral force, at least in the range where the vehicle does not spin. This is advantageous.

  In another aspect of the vehicle control apparatus according to the present invention to which a convergent steering force is applied, the convergent steering is based on a differential value of a lateral force acting on the front wheel and a proportional value of the lateral force acting on the rear wheel. It further comprises a convergence steering force determining means for determining a force, and the steering control means controls the steering force applying means so that the determined converged steering force is applied.

  According to this aspect, the differential value of the front wheel lateral force and the proportional value of the rear wheel lateral force are obtained by the convergent steering force determining means that can take the form of various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device. Since the convergence steering force is determined based on the above, the convergence steering force can be suitably determined.

  In another aspect of the vehicle control apparatus according to the present invention, the vehicle control device further includes a mutual ratio determining means for determining a mutual ratio of the braking force applied to each of the brakes so that the behavior is stabilized. The braking force applying means is controlled based on the determined mutual ratio during at least a part of the deceleration period of the vehicle.

  According to this aspect, for example, the mutual ratio determining means that can take the form of various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device, each of the wheels when being substituted for the application of a stabilizing steering force. The mutual ratio of braking forces is determined.

  When the mutual ratio of the braking force is changed, the moments around the kingpin axis in each wheel will be different for each wheel, and it is possible to turn the vehicle in a specific direction or turn the vehicle in a specific direction. Can be encouraged. Therefore, in this case, it is possible to obtain the same effect as that of urging steering of the front wheels by applying the stabilizing steering force or the convergent steering force by applying the braking force.

  Note that the manner of determining the mutual ratio according to the mutual ratio determining means is not limited as long as it can be substituted for the provision of the stabilizing steering force or the convergent steering force. For example, the mutual ratio of the convergent steering force and the braking force is previously limited. When it is possible to associate ratios one-to-one, one-to-many, many-to-one, or many-to-many experimentally, empirically, or based on simulations or numerical calculations, such a correspondence relationship is used. The mutual ratio may be determined by appropriately selecting a value corresponding to the stabilized steering force or the convergent steering force to be applied from the represented map, or a process for obtaining such a stabilized steering force or the convergent steering force. Without going through the above, the mutual ratio may be determined individually and specifically each time as a result of a numerical operation based on an appropriate algorithm or calculation formula set in advance.

  In another aspect of the vehicle control device according to the present invention, a second specifying means for specifying a load state of the power supply device and whether or not the power supply device is in a high load state based on the specified load state. The braking control means is provided to each of the power instead of the stabilizing steering force when the power supply device is in the high load state during the deceleration period of the vehicle. The braking force applying means is controlled so that the behavior is stabilized by the braking force.

  According to this aspect, detection is made by, for example, an SOC (State Of Charge) sensor or the like by the action of the second specifying means that can take the form of various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device. The load state of the power supply device is specified based on various index values such as the SOC and SOH (degraded state) of the power supply device to be operated, or the operation states of various auxiliary machines that are loads of the power supply device in the vehicle, for example.

  Further, it is determined whether or not the power supply device is in a high load state based on the specified load state by a determination means that can take the form of various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device. Is done.

  Here, the “high load state” can be predicted to be a load state that may be accompanied by practical difficulties in applying a stabilized steering force to be used for behavior control of the vehicle, or to fall into such a state in the near future. It is a concept that encompasses load states that can be defined as prohibiting the application of a stabilizing steering force from a realistic, objective or rational viewpoint, such as a load state.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

<Embodiment of the Invention>
Hereinafter, an embodiment according to a vehicle control device of the present invention will be described with reference to the drawings as appropriate.

<Configuration of Embodiment>
First, with reference to FIG. 1, the structure of the vehicle 10 which concerns on one Embodiment of this invention is demonstrated. FIG. 1 is a schematic configuration diagram conceptually showing the basic configuration of the vehicle 10.

  As shown in FIG. 1, the vehicle 10 includes a left front wheel FL and a right front wheel FR, and a left rear wheel RL and a left rear wheel RR, and at least one of the front wheel and the rear wheel obtains a driving force of an engine (not shown). And the vehicle can travel in a desired direction by steering the front wheels.

  The vehicle 10 includes an ECU 100 and an EPS 200. The ECU 100 is an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory) (not shown), and is configured to be able to control the entire operation of the vehicle 10. 1 is an example of a “vehicle control device” according to the present invention. The ECU 100 is configured to be able to execute various processes to be described later for controlling the operation of the EPS 200 and the operation of each unit associated therewith.

  The EPS 200 is a so-called electric power steering device, and is configured to be able to steer the front wheels FL and FR, which are steered wheels, according to the operation of the steering wheel 11 by the driver. It is an example of “giving means”.

  The EPS 200 employs a rack-and-pinion type steering method, a steering shaft 12 having one end connected to the steering wheel 11, and a rack-and-pinion connected to the other end of the steering shaft 12. And a mechanism 13. The EPS 200 may employ other steering methods.

  The rack and pinion mechanism 13 is configured to be able to convert a force in the rotational direction of the steering shaft 12 into a force in the reciprocating direction of the rack bar 14. Further, both ends of the rack bar 14 are connected to the front wheels FL and FR via tie rods (not shown), and the directions of the front wheels FL and FR are changed in accordance with the reciprocating motion of the rack bar 14. .

  The EPS 200 further detects a steering angle MT configured to be able to detect a steering angle θ, which is a rotation angle of the steering wheel 11, and a steering torque MT applied to the steering shaft 12 through the operation of the steering wheel 11. The torque sensor 17 is configured to be capable of generating an auxiliary steering force that reduces the operation burden on the driver, and the auxiliary steering force can be applied to the steering shaft 12 via a reduction gear (not shown). The electric motor 18 is provided. The steering angle sensor 16 and the torque sensor 17 are electrically connected to the ECU 100, respectively, and the detected steering angle θ and the steering torque MT are constantly grasped by the ECU 100. The electric motor 18 is electrically connected to the ECU 100 via a motor control system (not shown), and the operation state is controlled by the ECU 100.

  The vehicle 10 includes a roll angle calculation circuit 19, a vehicle speed sensor 20, a lateral force sensor 21, and a tack-in determination circuit 22. The roll angle calculation circuit 19 is configured to be able to calculate the roll angle RA of the vehicle 10 based on the lateral acceleration of the vehicle 10 detected by a lateral G sensor (not shown). Further, the calculated roll angle RA is grasped by the ECU 100 electrically connected to the roll angle calculation circuit 19.

  The vehicle speed sensor 19 is a sensor configured to be able to detect the speed (hereinafter referred to as “vehicle speed”) V of the vehicle 10. The lateral force sensor 21 is a sensor configured to be able to detect a lateral force Ff of the front wheel and a lateral force Fr of the rear wheel in the vehicle 10. Each sensor is electrically connected to the ECU 100, and the vehicle speed V and the lateral forces Ff and Fr detected in each sensor are grasped by the ECU 100.

  The tuck-in determination circuit 22 determines whether or not tuck-in has occurred in the vehicle 10 based on the yaw rate γ and the throttle opening O of the vehicle 10 detected by a yaw rate sensor and a throttle opening sensor (not shown). The control signal S1 indicating whether or not tuck-in has occurred is output to the electrically connected ECU 100.

  In the vehicle 10, the lateral forces Ff and Fr are directly detected by the lateral force sensor 21. Instead of providing the lateral force sensor 21, for example, the ECU 100 calculates the lateral forces Ff and Fr based on other parameters. It may be configured to estimate (in other words, calculate) by, for example. Similarly, the various other sensors may be configured to directly detect the detection target of the sensor by providing the sensor, or instead of providing the sensor, for example, the ECU 100 may be based on other parameters. The detection target of the sensor may be estimated by calculation or the like.

  On the other hand, each wheel in the vehicle 10 is provided with a corresponding wheel cylinder 15FL, 15FR, 15RL and 15RR. Each wheel cylinder is configured to be able to apply a driving force corresponding to a supplied hydraulic pressure to a braking member (not shown), and each wheel receives a braking force corresponding to this driving force. It is the structure transmitted via a member.

  The hydraulic pressure supplied to each wheel cylinder is controlled by the brake actuator 23. The brake actuator 23 is a master cylinder connected to a brake pedal (not shown), various pipes for distributing the hydraulic pressure given by the master cylinder to each wheel cylinder, and the hydraulic pressure transmitted to each wheel cylinder is individually increased and reduced. The operation of each part is controlled by the ECU 100 that is electrically connected to the brake actuator 23. That is, in the vehicle 10, the braking force acting on each wheel can be controlled independently of the driver's brake operation, and each wheel cylinder and the brake actuator 23 constitute an example of so-called ECB. . In the following description, the term “ECB” is appropriately used as a term indicating the entire electronically controlled brake system in the vehicle 10.

  The battery 24 is an example of a “power supply device” according to the present invention configured to be able to supply power to the above-described EPS 200 and ECB. The battery 24 is also configured to function as a power source for various auxiliary devices of the vehicle 10 such as an air conditioner, cigar lighter, various lights, and a car navigation device (not shown in FIG. 1). It takes the form of a 12 volt battery or the like.

  The battery 24 is provided with an SOC sensor 25. The SOC sensor 24 is configured to be able to detect the state of charge of the battery 24 (in this embodiment, it is equivalent to the remaining battery level and is an example of a “load state” according to the present invention). The state of charge of the battery is configured to be output to the ECU 100 electrically connected to the SOC sensor 25 as a control signal representing the state of charge.

<Operation of Embodiment>
<Basic operation of EPS 200>
In the vehicle 10, the EPS 200 reduces the driver's steering burden. Specifically, the ECU 100 controls the steering angle θ output from the steering angle sensor 16, the steering torque MT output from the torque sensor 17, the roll angle RA of the vehicle 10 output from the roll angle calculation circuit 19, the vehicle speed sensor 20. The vehicle speed V output from the vehicle, the lateral force Ff of the front wheels output from the lateral force sensor 21, the lateral force Fr of the rear wheels, and the control signal S1 indicating whether or not tack-in output from the tack-in determination circuit 22 is generated. Based on this, a target steering torque Ta that is a torque to be generated by the electric motor 18 is calculated.

  The ECU 100 controls a motor control system (not shown) so that a current corresponding to the calculated target steering torque Ta is supplied to the electric motor 18, and the electric motor 18 is driven. As a result, a steering assist force is applied from the electric motor 18 to the steering shaft 12, and as a result, the driver's steering burden is reduced. Further, the rack and pinion mechanism 13 converts the force in the rotational direction of the steering shaft 12 into the force in the reciprocating direction of the rack bar 14.

<Steering torque control by EPS200>
Next, the operation of the EPS 200 according to the present embodiment will be described in more detail with reference to FIGS.

  FIG. 2 is a flowchart conceptually showing the entire operation of the EPS 200. As shown in FIG. 2, when the ignition is turned off (step S100: NO), the process is substantially controlled in a standby state, and when the ignition is turned on (step S100: YES), The EPS 200 is activated.

  Specifically, the target steering torque Ta is calculated by the operation of the ECU 100 (step S200), and the steering torque control is performed by driving the electric motor 18 in accordance with the calculated target steering torque Ta (step S200). S300).

  FIG. 3 is a flowchart showing the calculation operation of the target steering torque Ta in step S200 of FIG. As shown in FIG. 3, when calculating the target steering torque Ta, it is first determined whether or not the steering is in an overshoot state (or there is a possibility of being in an overshoot state) (step S210). . In other words, the vibration of the steering and the yaw vibration of the vehicle are coupled to each other, and it is determined whether or not the vehicle 10 is in a wobbling state (or may be wobbling). Note that the overshoot state determination operation in step S210 will be described in detail later with reference to FIG.

  As a result of the determination in step S210, when it is determined that the steering is not in the overshoot state (or the steering is not likely to be in the overshoot state) (step S210: NO), refer to FIG. 6 and FIG. However, in a manner described in detail later, the basic steering torque Tb is calculated as the target steering torque Ta (step S230).

  On the other hand, as a result of the determination in step S210, if it is determined that the steering is in an overshoot state (or the steering may be in an overshoot state) (step S210: YES), then, by the driver A reverse assist determination is performed to determine whether or not the steering direction of the steering wheel 11 is opposite to the direction of the steering force applied to the front wheels FL and FR (that is, reverse assist) (step S220). The reverse assist determination operation in step S220 will be described in detail later with reference to FIG.

As a result of the determination in step S220, when it is determined to be reverse assist (step S220: YES), the basic steering torque Tb is calculated as the target steering torque Ta (step S230).

  On the other hand, as a result of the determination in step S220, when it is determined that it is not reverse assist (step S220: NO), the convergence steering torque Tc is calculated as the target steering torque Ta (step S240). The convergence steering torque Tc will be described later. When the basic steering torque Tb or the convergent steering torque Tc is calculated as the target steering torque Ta, the calculation operation of the target steering torque Ta according to step S200 ends.

  FIG. 4 is a flowchart showing the overshoot state determination operation in step S210 of FIG. As shown in FIG. 4, when the overshoot state is determined, first, whether the ratio of the lateral force Fr of the rear wheels RL and RR to the steering angle δ of the front wheels FL and FR is greater than a predetermined threshold value OS1. Is determined (step S211).

  If the result of determination in step S211 is that the ratio of the lateral force Fr of the rear wheels RL and RR to the steering angle δ of the front wheels FL and FR is greater than the threshold value OS1 (step S211: YES), steering is performed. It is determined that the camera is in an overshoot state (step S214).

  On the other hand, as a result of the determination in step S211, when it is determined that the ratio of the lateral force Fr of the rear wheels RL and RR to the steering angle δ of the front wheels FL and FR is not larger than the threshold value OS1 (step S211: NO). Subsequently, it is determined whether or not the ratio of the roll angle RA to the steering angle δ of the front wheels FL and FR is greater than a predetermined threshold value OS2 (step S212).

  As a result of the determination in step S212, when it is determined that the ratio of the roll angle RA to the steering angle δ of the front wheels FL and FR is larger than the threshold value OS2 (step S212: YES), it is determined that the steering is in an overshoot state. (Step S214).

  On the other hand, as a result of the determination in step S212, when it is determined that the ratio of the roll angle RA to the steering angle δ of the front wheels FL and FR is not larger than the threshold value OS2 (step S212: NO), the steering is in an overshoot state. It is determined that there is no (that is, the steering is stable) (step S213). Therefore, the basic steering torque Tb is calculated as the target steering torque Ta.

  In addition to or instead of the determination in step S211, is the ratio of the lateral force Fr of the rear wheels RL and RR to the lateral force Ff of the front wheels FL and FR (that is, Fr / Ff) greater than a predetermined threshold value OS3? It may be configured to determine whether or not. In this case, when it is determined that the ratio of the lateral force Fr of the rear wheels RL and RR to the lateral force Ff of the front wheels FL and FR is larger than the threshold value OS3, it is determined that the steering is in an overshoot state. If it is determined that the ratio of the lateral force Fr of the rear wheels RL and RR to the lateral force Ff of the front wheels FL and FR is not greater than the threshold value OS3, the determination in step S212 is subsequently performed.

  The threshold values OS1, OS2, and OS3 are hysteresis loops of the steering angle δ of the front wheels FL and FR and the lateral force Fr of the rear wheels RL and RR, and the hysteresis loop of the steering angle δ and the roll angle RA of the front wheels FL and FR. And hysteresis loops of the lateral force Fr of the rear wheels RL and RR with respect to the lateral force Ff of the front wheels FL and FR (particularly, a hysteresis loop when the vehicle speed is relatively low and a hysteresis loop when the vehicle speed is relatively high). Based on the various characteristics of the vehicle 10 and the like, an appropriate value is set for each vehicle 10 equipped with the EPS 200 experimentally, empirically, mathematically or theoretically, or using simulation. Is preferred. However, the setting mode is not limited as long as it is a threshold that can suitably determine whether or not the steering is in an overshoot state.

  FIG. 5 is a flowchart showing the reverse assist determination operation in step S220 of FIG. As shown in FIG. 5, when reverse assist is determined, first, the steering direction of the steering wheel 11 by the driver and the direction in which the steering force applied by the electric motor 18 steers the front wheels FL and FR are reversed. It is determined whether or not (step S221).

  As a result of the determination in step S221, when it is determined that the steering direction of the steering wheel 11 by the driver is opposite to the direction in which the steering force applied by the electric motor 18 steers the front wheels FL and FR (step S21). S221: YES) Subsequently, it is determined whether or not the ratio of the lateral force Fr of the rear wheels RL and RR to the steering angle δ of the front wheels FL and FR is greater than a predetermined threshold value OS4 (step S225). Specifically, it is determined whether or not steering vibration is occurring. For this reason, the threshold value OS4 is larger than the above-described threshold value OS1. Further, for OS4, experimental, empirical, mathematical, etc., taking into account various characteristics of the vehicle 10 based on a hysteresis loop of the steering angle δ of the front wheels FL and FR and the lateral force Fr of the rear wheels RL and RR. It is preferable that a suitable value is set for each vehicle 10 provided with the EPS 200, manually or theoretically or using simulation or the like. However, the setting mode is not limited as long as it is a threshold value that can suitably determine whether or not steering vibration is occurring.

  As a result of the determination in step S225, when it is determined that the ratio of the lateral force Fr of the rear wheels RL and RR to the steering angle δ of the front wheels FL and FR is larger than the threshold value OS4 (step S225: YES), there is no reverse assist. Is determined (step S226). Therefore, the convergence steering torque Tc is calculated as the target steering torque Ta.

  On the other hand, as a result of the determination in step S225, when it is determined that the ratio of the lateral force Fr of the rear wheels RL and RR to the steering angle δ of the front wheels FL and FR is not larger than the threshold value OS4 (step S225: NO), It is determined that it is reverse assist (step S227). Therefore, the basic steering torque Tb is calculated as the target steering torque Ta.

  On the other hand, if it is determined as a result of the determination in step S221 that the steering direction of the steering wheel 11 by the driver and the direction in which the steering force applied by the electric motor 18 steers the front wheels FL and FR are not reversed ( Step S221: NO) Subsequently, whether or not the absolute value of the steering angle θ of the steering wheel 11 is smaller than the predetermined threshold value OS5_1 and the absolute value of the steering speed of the steering wheel 11 (that is, the steering angular velocity dθ) are the predetermined threshold value. It is determined whether it is smaller than OS5_2 (step S222).

  As a result of the determination in step S222, when it is determined that the absolute value of the steering angle θ of the steering wheel 11 is smaller than the threshold value OS5_1 and the absolute value of the steering speed dθ of the steering wheel 11 is smaller than the threshold value OS5_2 (step S222: YES) ), It is determined to be reverse assist (step S227). Therefore, the basic steering torque Tb is calculated as the target steering torque Ta.

  Even if the absolute value of the steering angle θ of the steering wheel 11 is not smaller than the threshold value OS5_1, if the absolute value of the steering speed dθ of the steering wheel 11 is smaller than the threshold value OS5_2, it may be determined that the assist is reverse assist. Good. Further, even if the absolute value of the steering speed dθ of the steering wheel 11 is not smaller than the threshold value OS5_2, if the absolute value of the steering angle θ of the steering wheel 11 is smaller than the threshold value OS5_1, it may be determined that it is reverse assist. Good.

  On the other hand, if it is determined in step S222 that the absolute value of the steering angle θ of the steering wheel 11 is not smaller than the threshold value OS5_1 or the absolute value of the steering speed dθ of the steering wheel 11 is not smaller than the threshold value OS5_2. (Step S222: NO) Subsequently, whether the absolute value of the steering angle θ of the steering wheel 11 is larger than a predetermined threshold value OS6_1 and whether the absolute value of the steering speed dθ of the steering wheel 11 is larger than a predetermined threshold value OS6_2. Is determined (step S223).

  As a result of the determination in step S223, when it is determined that the absolute value of the steering angle θ of the steering wheel 11 is larger than the threshold value OS6_1 and the absolute value of the steering speed dθ of the steering wheel 11 is larger than the threshold value OS6_2 (step S223: YES). ), It is determined to be reverse assist (step S227). Therefore, the basic steering torque Tb is calculated as the target steering torque Ta.

Even if the absolute value of the steering angle θ of the steering wheel 11 is not larger than the threshold value OS6_1, if the absolute value of the steering speed dθ of the steering wheel 11 is larger than the threshold value OS6_2, it may be determined that the assist is reverse assist. Good. Further, even if the absolute value of the steering speed dθ of the steering wheel 11 is not larger than the threshold value OS6_2, if the absolute value of the steering angle θ of the steering wheel 11 is larger than the threshold value OS6_1, it is determined that it is reverse assist. Good.

  On the other hand, as a result of the determination in step S223, when it is determined that the absolute value of the steering angle θ of the steering wheel 11 is not larger than the threshold value OS6_1, or the absolute value of the steering speed dθ of the steering wheel 11 is not larger than the threshold value OS6_2. (Step S223: NO) Subsequently, it is determined whether or not the vehicle 10 is in a tuck-in state (or is likely to be in a tuck-in state) (step S224). Such a determination is performed based on the control signal S1 output from the tack-in determination circuit 22.

As a result of the determination in step S224, if it is determined that the vehicle is in the tuck-in state (or may be in the tuck-in state) (step S224: YES), it is determined that the assist is in reverse (step S227). . Therefore, the basic steering torque Tb is calculated as the target steering torque Ta.

  On the other hand, as a result of the determination in step S224, if it is determined that the vehicle is not in the tuck-in state (or that there is no possibility of being in the tuck-in state) (step S224: NO), it is determined that the vehicle is not reverse assist (step S226). ). Therefore, the convergence steering torque Tc is calculated as the target steering torque Ta.

  Note that the thresholds OS5_1, OS5_2, OS6_1, and OS6_2 are also experimentally, empirically, mathematically, theoretically, or by using a simulation or the like while considering various characteristics of the vehicle 10 for each vehicle 10 provided with the EPS 200. It is preferable that a suitable value is set.

  FIG. 6 is a flowchart showing the calculation operation of the basic steering torque Tb in step S230 of FIG. As shown in FIG. 6, when the basic steering torque Tb is calculated, first, various signals (for example, the vehicle speed V, the steering torque MT, etc.) necessary for calculating the basic steering torque Tb are read (step S231). . Subsequently, the basic steering torque Tb is calculated based on the various signals read in Step 231 (Step S232).

  Specifically, the basic steering torque Tb is calculated based on a graph showing the relationship between the steering torque MT and the basic steering torque Tb shown in FIG. In order to secure play of the steering wheel 11, the basic steering torque Tb is calculated as 0 when the steering torque MT is relatively small. When the steering torque MT becomes a certain level, a larger basic steering torque Tb is calculated as the steering torque MT increases. When the steering torque MT is greater than a predetermined value, a constant basic steering torque Tb that does not vary depending on the magnitude of the steering torque MT is calculated. At this time, the basic steering torque Tb may be reduced as the vehicle speed V increases.

  Next, the calculation operation of the convergence steering torque Tc in step S240 will be described. When calculating the convergence steering torque Tc, the ECU 100 first sets vehicle speed dependent coefficients KV1 and KV2.

Specifically, the vehicle speed dependency coefficient KV1 is set based on the graph showing the relationship between the vehicle speed dependency coefficient KV1 and the vehicle speed V shown in FIG. Similarly, the vehicle speed dependency coefficient KV2 vs. vehicle speed V shown in FIG.
A vehicle speed dependency coefficient KV2 is set based on the graph showing the relationship.

  The vehicle speed dependent coefficients KV1 and KV2 shown in FIGS. 8 and 9 can be obtained using an equation of motion indicating the motion of the vehicle 10 in the plane direction. Specifically, the moment of inertia of the vehicle 10 is I, the distance from the front axis to the center of gravity of the vehicle 10 is Lf, the distance from the rear axis to the center of gravity of the vehicle 10 is Lr, and the trail amount is Lt. Assuming that the slip angle of the vehicle 10 is β, the cornering power on the front wheel side is Kf, and the cornering power on the rear wheel side is Kr, the equation of motion of the vehicle 10 is expressed by equations (1) to (4). In the following equations, “d ()” represents the differential value of (). For example, dγ represents a differential value of γ.

I · dγ = Ff · Lf−Fr · Lr (1)
m · V · (dβ + γ) = Ff + Fr (2)
Ff = 2Kf · (δ−β−Lf / V · γ) (3)
Fr = 2Kr · (−β + Lr / V · γ) (4)
Further, in the present embodiment, since EPS 200 performs torque input, assuming that the inertia moment of front wheels FL and FR is Ih, the viscosity coefficient is Ch, and the steering torque is Th, the following equation (5) is obtained. To establish.

Ih · d (dδ) + Ch · dδ + Ff · Lt = Th (5)
Using the formulas (1) to (5), when the target steering torque Ta is obtained with emphasis on suppressing yaw vibration of the vehicle 10 (in other words, increasing damping of the vehicle 10) (that is, (5 (By solving the equation obtained by adding the target steering torque Ta to the right side of the equation)) based on the lateral force Fr of the rear wheels RL and RR and the differential value of the lateral force Fr (here, the convergent steering torque Tc). ) Should be set. Specifically, the target steering torque Ta is multiplied by a value obtained by multiplying the lateral force Fr of the rear wheels RL and RR by a coefficient A and a coefficient B present by a differential value dFr of the lateral force Fr of the rear wheels RL and RR. It turns out that it may be set to the sum of the combined values. The coefficients A and B correspond to vehicle speed dependent coefficients KV1 and KV2, respectively. The vehicle speed dependence coefficients KV1 and KV2 obtained in this way vary depending on the vehicle speed V, as shown in FIGS.

  In particular, the sign of the vehicle speed dependency coefficient KV1 is inverted with a certain vehicle speed (specifically, a state where the vehicle is in a neutral steer) as a boundary. Specifically, the vehicle speed dependency coefficient KV1 below a certain vehicle speed takes a positive value, and the vehicle speed dependence coefficient above a certain vehicle speed takes a negative value. This is because the behavior of the vehicle tends to be oversteered at a certain vehicle speed or higher, and therefore, in order to suppress the oversteer (that is, to suppress the yaw vibration of the vehicle) Indicates that the target steering torque Ta is set in consideration of steering in the opposite direction (in other words, it is difficult for the driver to turn the steering wheel). That is, the target steering torque Ta is set so that the behavior of the vehicle 10 is stabilized.

  Thus, the convergence steering torque Tc as the target steering torque Ta can be calculated based on the equation KV1 · Fr + KV2 · dFr.

  When the vehicle speed V is abnormal (for example, when a hydroplaning phenomenon or the like occurs), it is preferable to set the vehicle speed dependency coefficient KV1 to zero.

  In this embodiment, the convergent steering torque Tc as described above is applied. However, depending on the behavior of the vehicle, the convergent steering torque Tc may be insufficient. In preparation for such a case, a coefficient corresponding to various situations of the vehicle 10 may be set, and the convergence steering force may be set more finely based on the coefficient.

  Specifically, for example, a rough road coefficient KB may be set. In this case, the rough road coefficient KB is set to a numerical value between 0 and 1, for example. When the vehicle 10 is traveling on a rough road (for example, a low μ road or a road surface with a large vehicle speed V such as an uneven road, which fluctuates irregularly or unintentionally), the rough road coefficient KB is, for example, 0. Is set. Alternatively, when the vehicle 10 is traveling on a rough road, the rough road coefficient KB may be set to a value greater than 0 and less than 1. On the other hand, when the vehicle 10 is not traveling on a rough road (that is, when traveling on a normal road such as a paved road), the rough road coefficient KB is set to 1, for example.

  For example, the longitudinal acceleration coefficient KA may be set. The longitudinal acceleration coefficient KA is set to a numerical value between 0 and 1, for example.

  In this case, the longitudinal acceleration coefficient KA is set to 1, for example, when the absolute value of the longitudinal acceleration of the vehicle 10 is not more than a predetermined value. When the absolute value of the longitudinal acceleration of the vehicle 10 is not more than a predetermined value, the longitudinal acceleration coefficient KA is set to a smaller value as the absolute value of the longitudinal acceleration of the vehicle 10 is larger. Alternatively, the longitudinal acceleration coefficient may be set to 0 when the absolute value of the longitudinal acceleration is equal to or greater than a predetermined value or when the vehicle 10 has a pitch.

  On the other hand, the longitudinal acceleration coefficient may be set according to the elapsed time from when the longitudinal acceleration starts to change. For example, when the longitudinal acceleration starts to change, the longitudinal acceleration coefficient is set to 0 until the time corresponding to the pitch period unique to the vehicle 10 has elapsed, and the time corresponding to the pitch period has elapsed. After that, it may be configured to gradually increase the value as time passes.

  For example, ABS coefficients KX1 and KX2 may be set. The ABS coefficients KX1 and KX2 are set to numerical values between 0 and 1, for example.

  In this case, each of the ABS coefficients KX1 and KX2 may be set to 0 when ABS control is performed, for example. The ABS control mentioned here is control that can be realized by the ECB provided in the present embodiment, and is detected by, for example, a wheel speed sensor (not shown in FIG. 1) provided in association with each wheel. This refers to control or the like that distributes braking force so that each wheel does not lock based on wheel speed or the like.

  After that, when the ABS control is finished, first, the ABS coefficient KX2 is gradually set to a large value, and after a certain time has passed since the ABS control was finished, the ABS coefficient KX1 is then gradually raised to a large value. Set. At this time, the increment per unit time of the ABS coefficient KX2 is larger than the increment per unit time of the ABS coefficient KX1.

  Instead of the operation of gradually increasing the ABS coefficient KX1 and the ABS coefficient KX2 after the ABS control is finished, the ABS coefficient KX2 is set to 1 and the ABS coefficient KX1 is set for a certain period after the ABS control is finished. May be set to 0, and the ABS coefficient KX1 may be set to 1 after a certain period of time has elapsed.

  Even when longitudinal force control such as VSC (Vehicle Stability Control) or TRC (TRaction Control) is performed, it is preferable to set the ABS coefficients KX1 and KX2 in the same manner as in the ABS control.

  Further, for example, a suspension coefficient KZ may be set. The suspension coefficient KZ is set to a numerical value between 0 and 1, for example.

  In this case, if the suspension control is not performed, the suspension coefficient KZ is set to 1, for example. On the other hand, when suspension control is being performed, the suspension coefficient KZ is set to 0 or a value greater than 0 and less than 1, for example.

Also, when the ground load variable control such as the stabilizer control is performed, it is preferable to set the suspension coefficient KZ in the same manner as in the suspension control.

  When such various coefficients are all set as described above, for example, a coefficient that is actually multiplied to the lateral force Fr of the rear wheels RL and RR by, for example, the following equation: K1 = KV1 × KB × KA × KX1 × KZ K1 may be calculated.

  Similarly, K2, which is a coefficient that is actually multiplied by the differential value dFr of the lateral force Fr of the rear wheels RL and RR, may be calculated by, for example, an equation of K2 = KV2 × KX2.

  Based on these K1 and K2, and the calculated lateral force Fr of the rear wheels RL and RR and the differential value dFr of the lateral force Fr of the rear wheels RL and RR, the convergence steering torque Tc may be calculated.

  As described above, according to the control of the steering torque according to the present embodiment, it can be suitably determined whether or not the steering is in an overshoot state. When the steering is in an overshoot state, the convergence steering torque Tc can be set as the target steering torque Ta.

  At this time, the convergent steering torque Tc is output from the electric motor 18 by the operation according to step S300 in FIG. 2, so that the moments around the kingpin axis in the left and right front wheels FL and FR are changed between the steering vibration and the yaw vibration of the vehicle. Since the coupling acts in a direction to converge, it prevents the steering vibration and yaw vibration from coupling to each other (specifically, resonating in the opposite phase) even when the steering is in an overshoot state. be able to. As a result, the vibrations of the front wheels FL and FR can be converged. That is, the convergence of the vehicle 10 can be improved while improving the convergence of the steering.

  In addition, since the convergence steering torque Tc is calculated based on the equation of motion in the plane direction of the vehicle 10 while taking into account the contribution due to torque input, the convergence steering torque Tc is calculated with high accuracy (or more optimal). can do.

  In addition, the steering is overshooted by monitoring the steering angle δ of the front wheels FL and FR, the lateral force Ff of the front wheels FL and FR, the lateral force Fr of the rear wheels RL and RR, the roll angle RA, etc. Whether or not there is can be determined suitably or with high accuracy.

  In particular, since the ratio of the roll angle RA to the steering angle δ of the front wheels FL and FR as shown in step S212 of FIG. 4 is monitored, for example, in a vehicle having a high vehicle height such as a minivan or SUV (Sport Utility Vehicle). In addition, it can be suitably or accurately determined whether or not the steering is in an overshoot state. In consideration of such advantages, the operation of step S212 in FIG. 4 is selectively performed on a vehicle having a high vehicle height, and for a vehicle having a low vehicle height such as a sports car type sedan or a coupe, for example, FIG. You may comprise so that operation | movement of step S212 may not be performed.

  Furthermore, as shown in step S221 of FIG. 5, when the steering direction by the driver and the direction in which the steering force applied by the electric motor 18 steers the front wheels FL and FR are reversed, the driver Considering that there is a high possibility of performing avoidance steering, by setting the basic steering force Tb corresponding to the driver's steering to the target steering torque Ta, deterioration of avoidance performance can be prevented. That is, it is possible to respect the driver's intention to avoid emergency.

  However, even if the steering direction by the driver and the steering force applied by the electric motor 18 are opposite to the direction in which the front wheels FL and FR are steered, as shown in step S225 of FIG. If or has occurred, the stability of the vehicle 10 can be more important than the steering feeling by setting the convergence steering torque Tc to the target steering torque Ta.

  In the case where the steering direction by the driver and the steering force applied by the electric motor 18 are opposite to the direction in which the front wheels FL and FR are steered, the steering force in the direction opposite to the steering direction by the driver. The coefficient KV1 (or K1) to be multiplied by the lateral force Fr of the rear wheels RL and RR may be reduced. The contribution ratio of the proportional value of the lateral force Fr of the rear wheels RL and RR when calculating the convergence steering torque Tc may be reduced.

  Further, according to the present embodiment, as shown in step S222 of FIG. 5, the driver can easily feel a change in steering feeling in a range where the absolute value of the steering angle θ and the absolute value of the steering speed dθ are relatively small. In consideration of this, by setting the basic steering torque Tb corresponding to the steering torque MT as the target steering torque Ta, the driver's steering feeling is not deteriorated.

  Further, as shown in step S223 of FIG. 5, it is considered that the driver may be performing emergency avoidance steering in a range where the absolute value of the steering angle θ and the absolute value of the steering speed dθ are relatively large. Thus, by setting the basic steering torque Tb corresponding to the steering torque MT as the target steering torque Ta, the driver's intention to avoid emergency can be respected.

Furthermore, as shown in step S224 of FIG. 5, when tuck-in has occurred, the lateral force Fr of the rear wheels RL and RR is likely to fluctuate due to tuck-in or desired by steering the front wheels FL and FR. Considering that the lateral force Fr is not always obtained, the basic steering torque Tb corresponding to the steering torque MT can be set as the target steering torque Ta.

  Further, depending on the setting mode of the convergence steering torque Tc, when the vehicle 10 is traveling on a rough road, the calculation of the convergence steering torque Tc of the differential value dFr of the lateral force Fr of the rear wheels RL and RR with large noise is performed. Is reduced or reduced to 0 (in other words, the convergent steering torque Tc is calculated based on the lateral force Fr of the rear wheels RL and RR with low noise), thereby eliminating the influence of the rough road as much as possible. The steering torque Tc can be suitably calculated.

  Furthermore, depending on the setting mode of the convergence steering torque Tc, when the vehicle 10 is accelerating / decelerating, the calculation of the convergence steering torque Tc of the lateral force Fr of the rear wheels RL and RR that varies greatly due to acceleration / deceleration is performed. Is reduced or reduced to 0 (in other words, the convergence steering torque Tc is calculated based on the differential value dFr of the lateral force Fr of the rear wheels RL and RR that does not vary greatly even by acceleration / deceleration). The convergence steering torque Tc can be suitably calculated while eliminating the influence of.

  Further, depending on the setting mode of the convergence steering torque Tc, when the longitudinal force control such as the ABS control is performed on the vehicle 10, the sideways of the rear wheels RL and RR that greatly vary due to the longitudinal force control are obtained. The contribution ratio of the force Fr to the calculation of the convergent steering torque Tc is reduced or reduced to 0 (in other words, the convergent steering is performed based on the differential value dFr of the lateral force Fr of the rear wheels RL and RR that does not vary so much even by the longitudinal force control). By calculating the torque Tc), the convergence steering torque Tc can be suitably calculated while eliminating the influence of the longitudinal force control as much as possible.

  Further, depending on the setting mode of the convergence steering torque Tc, when the ground load variable control such as the suspension control is performed, the convergence of the lateral force Fr of the rear wheels RL and RR that varies greatly due to the ground load control is achieved. Decreasing the contribution rate to the calculation of the steering torque Tc or setting it to 0 (in other words, the convergent steering torque Tc is set based on the differential value dFr of the lateral force Fr of the rear wheels RL and RR that does not vary so much even by the ground load variable control. Thus, the convergent steering torque Tc can be suitably calculated while eliminating the influence of the ground load variable control as much as possible.

  Furthermore, when the vehicle speed V is abnormal, the contribution ratio of the rear wheel RL and the lateral force Fr of the RR with large fluctuations to the calculation of the convergent steering torque Tc is reduced or reduced to 0 (in other words, the rear wheel RL with small fluctuations). And the convergent steering torque Tc is calculated based on the differential value dFr of the lateral force Fr of RR), the convergent steering torque Tc can be suitably calculated while eliminating the influence of the abnormality in the vehicle speed V as much as possible.

  In the above-described embodiment, the front wheels FL and FR are steered based on the steering torque MT and the target steering torque T. However, even in the case of so-called active steering where the front wheels FL and FR are steered by an actuator based on the steering angle θ, steering is performed in the same manner as the above operation when the steering is in an overshoot state. Thus, the various benefits described above can be enjoyed.

  By the way, the basic steering torque Tb or the convergent steering torque Tc is output from the electric motor 18 as the target steering torque Ta and the steering torque is controlled by the operation according to step S300 in FIG. Since the operation of the electric motor 18 becomes an electric load of the battery 24, the output of the basic steering torque Tb for the purpose of assisting the steering of the driver is aside from converging the coupling of the yaw vibration and the steering vibration. The application of the convergence steering torque Tc is difficult to execute depending on the load state of the battery 24.

  Therefore, in this embodiment, as shown in FIG. 10, the steering torque control according to step S300 is executed. FIG. 10 is a flowchart of the steering torque control according to step S300.

  In FIG. 10, the ECU 100 determines whether or not the target steering torque Ta is the convergence steering torque Tc (step S310). When it is not the convergent steering torque Tc, that is, when the target steering torque Ta is the basic steering torque Tb (step S310: NO), the ECU 100 controls the electric motor 18 to output the basic steering torque Tb (step S350).

  When the target steering torque Ta is the convergence steering torque Tc (step S310: YES), the ECU 100 determines whether or not the vehicle 10 is in a braking period (step S320). Whether or not the vehicle 10 is in the braking period can basically be determined by whether or not the brake pedal is operated. Or you may discriminate | determine whether the braking force is provided to each wheel from the operation state of the brake actuator 23, for example irrespective of operation of a brake pedal.

  When the vehicle 10 is not in the braking period (step S320: NO), the ECU 100 controls the electric motor 18 to output the convergent steering torque Tc (step S360). When the vehicle 10 is in a braking period (step S320: YES), the ECU 100 further determines whether or not the battery 24 is in a predetermined high load state (step S330).

  Whether or not the battery 24 is in a high load state is determined based on a control signal from the SOC sensor 25. More specifically, when the SOC of the battery 24 indicated by the control signal is less than a predetermined value, it is determined that the battery 24 is in a high load state. However, such a mode of determination is merely an example, and is output from the battery 24 based on the operating state of various auxiliary machines serving as the load of the battery 24 without depending on the control signal output from the SOC sensor 25. The determination relating to the high load state may be performed based on the voltage fluctuation state. That is, as long as it is possible to determine whether the current load state of the battery 24 is unfavorable for causing the electric motor 18 to output the convergent steering torque Tc using the electric power of the battery 24, the determination mode is as follows. This is not a limitation.

  When the battery 24 is not in a high load state (step S330: NO), the ECU 100 controls the electric motor 18 to output the convergent steering torque Tc (step S360).

  Even when the vehicle 10 is not in the braking period (step S320: NO), the battery 24 may be in a high load state. In such a case, the application of the convergent steering torque Tc according to step S360 may be prohibited regardless of whether it is difficult to apply the convergent steering torque Tc in practice. This is preferable because excessive use of the battery 24 can be restricted. At this time, the driver may be notified that the application of the convergent steering torque Tc is prohibited through a predetermined indicator or the like.

  On the other hand, when the battery 24 is in a high load state during the braking period (step S330: YES), the ECU 100 prohibits the torque output by the electric motor 18 and controls the moment around the kingpin axis by the converged steering torque Tc by the ECB. It substitutes by braking force distribution (step S340).

  Specifically, the ECU 100 is adapted in advance so as to obtain an effect similar to that obtained when the convergent steering torque Tc is applied to the front wheels experimentally, empirically, theoretically, or based on simulation or numerical calculation. The distribution ratio of the braking force corresponding to the value of the convergence steering torque Tc is determined based on the correspondence relationship between the value of the convergence steering torque Tc and the distribution ratio of the braking force applied to each wheel. Such alternative control is executed by controlling the brake actuator 23 based on the distribution ratio and the braking force originally required. When the process according to step S340, step S350, or step S360 is executed, the control of the steering torque according to step S300 ends.

  Here, with reference to FIG.11 and FIG.12, the detail of such alternative control by ECB is demonstrated. FIG. 11 is a schematic diagram for explaining a moment acting on one wheel (here, the left front wheel FL) in the vehicle 10 during braking.

  In FIG. 11, it is assumed that the braking force F is acting on the left front wheel FL. Here, if the distance (moment arm) from the kingpin axis KPFL corresponding to the left front wheel FL to the point of application of the braking force is Y, the moment around the kingpin axis KPFL acts in the left turning direction as shown in the figure, and its value Becomes F × Y. That is, the illustrated moment FY is obtained.

  FIG. 12 is a schematic conceptual diagram illustrating an example of alternative control by ECB. In the figure, the same reference numerals are given to the same portions as those in FIG. 11, and the description thereof will be omitted as appropriate.

  In FIG. 12, it is assumed that braking forces F1, F2, F3, and F4 are applied to the FL, FR, RL, and RR wheels, respectively. In this case, the moments acting around the corresponding kingpin axes KPFL, KPFR, KPRL, and KPRR are the moments F1Y, F2Y, F3Y, and F4Y, respectively.

  Here, it is assumed that the convergent steering torque Tc is output, for example, in a direction in which the front wheels are turned rightward in the drawing. In this case, as shown in the figure, the brake actuator 23 is controlled so that the braking force F2 is larger than the braking force F1, so that for the front wheels, the moment F2Y is larger than the moment F1Y, and the vehicle turns in the right turn direction. The moment of becomes relatively large. For this reason, it is possible to obtain the same effect as when the convergence steering torque Tc is applied in the right turn direction.

  On the other hand, for the rear wheels, the brake actuator 23 is controlled so that the braking force F3 is greater than the braking force F4, so that the moment F3Y is greater than the moment F4Y, and the moment in the left turn direction is relatively growing. When the steering vibration and the yaw vibration are coupled, the vibrations are in opposite phase, so the moment in the left turn direction should be relatively large on the rear wheel side, as opposed to the front wheel side. As a result, the coupling of the steering vibration and the yaw vibration in the vehicle 10 can be suitably suppressed.

  As described above, according to the present embodiment, for the braking period, by controlling the distribution of the braking force to each wheel provided in the vehicle 10, the same effect as that when the convergence steering torque Tc is applied to the front wheels can be obtained. For example, even when it is difficult to output the convergent steering torque Tc due to the load state of the battery 24, it is possible to suppress the coupling between the steering vibration and the yaw vibration as described above. That is, it is possible to reduce the influence of the load state of the power supply on the behavior of the vehicle.

  It should be noted that the distribution mode of the braking force in the ECB for converging the coupling between the steering vibration and the yaw vibration in the vehicle 10 converges the coupling to some extent as compared with the case where no such distribution is performed. As long as it is obtained, there is no limitation. For example, the distribution ratio may not be clarified in advance, and may be determined completely independently based on various control signals in the process of calculating the convergent steering torque Tc, for example.

  The present invention is not limited to the above-described embodiments, and can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. Is also included in the technical scope of the present invention.

1 is a schematic configuration diagram of a vehicle according to an embodiment of the present invention. It is a flowchart which shows the whole operation | movement of EPS in the vehicle of FIG. It is a flowchart which shows the operation | movement in step S200 of FIG. It is a flowchart which shows the operation | movement in step S210 of FIG. It is a flowchart which shows the operation | movement in step S220 of FIG. It is a flowchart which shows the operation | movement in step S230 of FIG. It is a graph which shows the relationship between steering torque and basic steering torque. It is a graph which shows the relationship between the vehicle speed dependence coefficient KV1 and vehicle speed. It is a graph which shows the relationship between the vehicle speed dependence coefficient KV2 and a vehicle speed. It is a flowchart which shows the operation | movement in step S300 of FIG. It is a schematic diagram explaining the moment which acts on one wheel at the time of braking. It is a schematic conceptual diagram showing an example which substitutes provision of a convergence steering torque by provision of braking force.

Explanation of symbols

  FL, FR, RL, RR ... wheels, 10 ... vehicle, 100 ... ECU, 200 ... EPS, 11 ... steering wheel, 12 ... steering shaft, 13 ... rack and pinion mechanism, 15FL, 15FR, 15RL, 15RR ... wheel cylinder, DESCRIPTION OF SYMBOLS 16 ... Steering angle sensor, 17 ... Torque sensor, 18 ... Electric motor, 19 ... Roll angle calculation circuit, 20 ... Vehicle speed sensor, 21 ... Side force sensor, 22 ... Tuck-in determination circuit, 23 ... Brake actuator, 24 ... Battery, 25 ... SOC sensor.

Claims (6)

A power supply device, a steering force applying means that is at least partially driven by electric power supplied from the power supply device and can apply a steering force to at least the front wheels, and a braking force application that can apply a braking force to each of the front wheels and the rear wheels A vehicle control device for controlling a vehicle provided with means,
First specifying means for specifying a predetermined index value associated with the state of behavior of the vehicle during steering of the front wheels;
Steering control for controlling the steering force applying means based on the specified index value so that a stabilizing steering force for steering the front wheels in a direction for stabilizing the behavior is applied as at least a part of the steering force. Means,
Braking control means for controlling the braking force applying means so that the behavior is stabilized by the braking force applied to each of the vehicles instead of the stabilizing steering force during at least a part of the deceleration period of the vehicle. A control apparatus for a vehicle. The first specifying means specifies an index value corresponding to a lateral force acting on the front wheel and an index value corresponding to a lateral force acting on the rear wheel as at least a part of the index value,
The steering control means converges the yaw vibration as the stabilized steering force when the ratio of the lateral force acting on the rear wheel to the lateral force acting on the front wheel is a ratio at which yaw vibration occurs in the vehicle. 2. The vehicle control device according to claim 1, wherein the steering force applying unit is controlled such that a convergent steering force for steering the front wheels is applied in a direction in which the front wheel is steered. The steering control means controls the steering force applying means so that the convergent steering force is applied when a ratio of a lateral force acting on the rear wheel to a lateral force acting on the front wheel is a predetermined value or more. The vehicle control device according to claim 2. A convergence steering force determination means for determining the convergence steering force based on a differential value of the lateral force acting on the front wheel and a proportional value of the lateral force acting on the rear wheel;
4. The vehicle control device according to claim 2, wherein the steering control unit controls the steering force applying unit so that the determined convergence steering force is applied. 5. And further comprising a mutual ratio determining means for determining a mutual ratio of the braking force applied to each of the behaviors so that the behavior becomes stable.
The braking control means controls the braking force applying means based on the determined mutual ratio during at least a part of the deceleration period of the vehicle. The vehicle control device described. Second specifying means for specifying a load state of the power supply device;
Determining means for determining whether or not the power supply device is in a high load state based on the specified load state;
When the power supply device is in the high load state during the deceleration period of the vehicle, the braking control unit is configured to stabilize the behavior by the braking force applied to each of the power instead of the stabilizing steering force. The vehicle control device according to any one of claims 1 to 5, wherein the braking force applying means is controlled.

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