JP2008126808A - Vehicular control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively curb operation of a steering wheel caused by torque-steering independently from a driver's steering condition. <P>SOLUTION: An ECU 100 executes torque-steering suppression processing in a vehicle 10 equipped with an EPS 200. In this processing, when the vehicle 10 is accelerating and the steering wheel 11 is in a hand-releasing state, assist torque ATRQ 1 at hand-releasing is output from a motor 17. When the steering wheel 11 is not in the hand-releasing state and predetermined permission conditions are satisfied, assist torque ATRQ 2 at steering is output from the motor 17 to compensate returning defects of the steering wheel 11 within the range of not inhibiting the steering operation by the driver. When steering is input while assist torque at the hand-releasing is output, switch processing is performed in accordance with each of turn and turn-back and the assist torque is gradually changed so as to suppress a sense of incongruity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technical field of a vehicle control device that controls a vehicle including, for example, an EPS (Electronic Control Power Steering).

  In this type of technical field, for example, a technique for compensating for a return failure of a steering wheel has been proposed (see, for example, Patent Document 1). According to the electric power steering device disclosed in Patent Document 1 (hereinafter referred to as “conventional technology”), the greater the estimated driver torque, the smaller the current command value of the motor. It is said that the return speed of the steering wheel can be made substantially constant regardless of whether the hand is lightly attached to the steering wheel, and the uncomfortable feeling given to the driver can be prevented.

  There is also disclosed a technique for changing the return correction current value by a minute current value in a direction approaching the target return correction current value to obtain the return current value (see, for example, Patent Document 2).

  A technique for calculating a base correction current value based on the target steering angular speed and the actual steering angular speed to obtain an assist target current is also disclosed (see, for example, Patent Document 3).

  A technique for compensating for a response delay due to inertia of an electric motor based on a differential value of steering torque has also been proposed (see, for example, Patent Document 4).

JP 2006-182051 A JP 2006-137281 A JP 2006-137359 A JP 2004-255934 A

  For example, in a front engine front drive (FF) vehicle or a four-wheel drive vehicle, for example, when a relatively large acceleration is applied to the vehicle, such as during start acceleration, torque steer is generated by the drive torque applied to the wheels. Sometimes. When torque steer occurs, the steering wheel is more easily operated regardless of the driver's intention and compared to the case of input from the road surface. Such steering wheel operation by torque steer can occur during hand-off or during steering, and it is a major factor that impedes the driving performance and comfort of the vehicle. There is a need. However, the conventional technique is based on a steady steering operation such as a steering angle range corresponding to the dead zone or a motor current being zero when the steering torque is large. It does not work effectively for the transient operation of the steering wheel. That is, the conventional technology has a technical problem that the running performance and comfort of the vehicle may be greatly impaired when torque steer occurs.

  The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide a vehicle control device that can effectively converge the steering wheel operation by torque steer regardless of the steering state of the driver. To do.

  In order to solve the above-described problems, a vehicle control apparatus according to the present invention includes auxiliary steering force applying means capable of applying an auxiliary steering force for assisting a steering force applied to a wheel via a steering wheel. A control device for a vehicle that controls a vehicle, a determination unit that determines whether or not the vehicle is in a predetermined acceleration state, and a binary state that indicates whether or not the steering wheel is artificially operated. The auxiliary steering force is applied to the wheel based on the specified operation state when it is determined that the operation state of the steering wheel includes at least specifying means for determining that the vehicle is in the acceleration state. And a control means for controlling the auxiliary steering force applying means so that a predetermined convergent steering force for directing the steering wheel toward the neutral position is applied. And features.

  In the present invention, the “auxiliary steering force applying means” assists a steering force applied by a driver or the like via a steering wheel to a wheel to be steered (hereinafter referred to as “steering wheel” as appropriate). It is a concept encompassing means capable of applying an auxiliary steering force, and as long as such a concept is secured, for example, an electrical, mechanical, or physical aspect of the auxiliary steering force applying means is not limited.

  The steering force described here refers to the steering torque applied via the steering wheel or the steering torque further constitutes a steering device including the steering wheel, for example, a steering shaft, a rack and pinion type, or a ball nut. A steering mechanism that can take various aspects such as a formula, and a physical force that is converted through a tie rod or the like as appropriate to move the steering wheel in the left-right direction. Therefore, the auxiliary steering force may be, for example, a motor torque output from an electric motor such as a motor, or the auxiliary torque that increases or decreases the above-described physical force obtained by appropriately converting such a motor torque. It may be a physical force.

  According to the vehicle control device of the present invention, when the operation is performed, the discriminating means which can take the form of various processing units such as an ECU (Electronic Control Unit), various controllers, various computer systems such as a microcomputer device, or the like. Thus, it is determined whether or not the vehicle is in a predetermined acceleration state.

  Here, the “predetermined acceleration state” according to the present invention is a concept encompassing acceleration states associated with the occurrence of torque steer, for example, experimentally, empirically, theoretically, or simulation in advance. Based on the above, the occurrence of torque steer that cannot be ignored in practice, or the acceleration state that supports the near future generation of such torque steer, or a constant or indefinite margin for such acceleration state Thus, an acceleration state determined from the viewpoint of preventing torque steer may be used.

  Here, “torque steer” refers to steering by a drive torque transmitted through a drive system including an internal combustion engine such as an engine, a drive shaft, a differential, an axle, and the like at the time of relatively rapid acceleration. This is a concept encompassing a phenomenon in which the wheel is moved, for example, to the left and right, and the steering wheel is finally operated independently of the driver's intention through the various parts of the steering device as described above. Therefore, the vehicle according to the present invention is a vehicle in which driving force is transmitted to at least the steering wheel, and preferably refers to an FF vehicle, a four-wheel drive vehicle, or the like.

  The aspect relating to the determination of whether or not the vehicle is in a predetermined acceleration state in the determination means is not limited as long as the determination is possible. For example, acceleration in the vehicle longitudinal direction (hereinafter referred to as “front and rear G” as appropriate). At least part of the vehicle speed (hereinafter referred to as “vehicle speed” as appropriate), the throttle valve opening in the internal combustion engine (hereinafter referred to as “throttle opening” as appropriate), and the driving torque of the vehicle. It may be determined based on. Note that torque steer depends on the physical or mechanical configuration of the vehicle, such as the arrangement of the internal combustion engine in the vehicle and the drive system, particularly the length of the left and right drive shafts. The reference may be set individually and specifically for each vehicle.

  On the other hand, apart from the determination as to whether or not the vehicle is in the predetermined acceleration state, according to the vehicle control device of the present invention, for example, various processing units such as ECU, various controllers or various computer systems such as a microcomputer device The operating state of the steering wheel is specified by specifying means that can take the form of the above.

  Here, the “operation state” according to the present invention is a concept including at least a binary state indicating whether or not the steering wheel is artificially operated. For example, as long as the concept is secured, for example, the steering wheel This means that a more detailed state may be included, including a quantitative indicator of how much the user has been manually manipulated.

  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 derivation or estimation according to a calculation formula or the like, or simply acquiring a value detected, selected, estimated or derived as an electric signal or the like.

  As a result of the determination of the acceleration state and the identification of the steering wheel operation state as described above, when it is determined that the vehicle is in the acceleration state, for example, various processing units such as an ECU, various controllers, microcomputer devices, etc. The control means that can take the form of a computer system or the like controls the auxiliary steering force applying means so that the convergent steering force is applied as the above-described auxiliary steering force based on the specified operation state.

  Here, the “convergence steering force” according to the present invention is an auxiliary steering force that moves the steering wheel toward the neutral position, in other words, an auxiliary steering force that acts in a direction to cancel the torque steer. The “neutral position” is an operation position of the steering wheel that allows the vehicle to travel straight, and preferably refers to a position at or near zero degrees as a steering angle. However, even if the neutral position can be defined by the steering angle in this way, the convergent steering force does not necessarily have the steering angle as the target value. That is, the steering wheel is attracted to the neutral position by the auxiliary steering force, in other words, as long as the operation of the steering wheel to the notch side is considerably hindered against the driver's intention, the convergent steering force The aspect relating to the provision of the steering wheel may be free, and the steering wheel may not necessarily be operated toward the neutral position only by the auxiliary steering force.

  According to the operation of such control means, when torque steer occurs in real time, or when near-future torque steer is predicted to occur, based on the steering wheel operation state at that time, For example, the above-described convergent steering force is applied to the wheel in accordance with a binary state (i.e., corresponding to the above-described binary state) that states whether the vehicle is in a released state or at least steered. Therefore, for example, when it is determined that the steering wheel is in the released state (that is, equivalent to a state where the steering wheel is not manually operated) and the vehicle is in an accelerated state such as suddenly starting, For example, a relatively large converging steering force that can suppress or converge the steering operation by torque steer or avoid the occurrence of such torque steer itself is applied.

  On the other hand, when torque steer occurs, the required convergence steering force can vary greatly depending on the operating state of the steering wheel. For example, if the steering wheel is at least in a steered state (i.e. equivalent to an artificially operated state), an artificial steering wheel that can be made to converge or avoid torque steer A convergent steering force only needs to be applied in the direction of assisting the operation, and a relatively small convergent steering force is often required as compared with the case of releasing the hand. On the contrary, if the convergent steering force in the released state is applied in such a case, it is easy to give an uncomfortable feeling that the steering wheel returns too much. Therefore, by applying the convergent steering force based on the operation state of the steering wheel, it is practically beneficial to avoid a sense of incongruity that can be given to the driver while suppressing a decrease in driving performance and comfort due to torque steer. Effects are provided.

  As described above, according to the vehicle control apparatus of the present invention, the driver is provided with an appropriate convergent steering force when torque steer that makes the behavior of the vehicle transiently unstable or before the occurrence of torque steer. It is possible to suppress or avoid the operation of the steering wheel unrelated to the intention. In other words, the steering wheel operation by torque steer can be effectively converged regardless of the steering state of the driver.

  It should be noted that the mode of control according to the control means may be freely determined within a range that does not at least inhibit the above-described effect according to the present invention. For example, the application characteristic of the convergent steering force is experimentally and empirically in advance, Theoretically, based on simulations, etc., so that the convergent steering force is applied as quickly as possible in the hand-off state, and the steering operation can be assisted without giving the driver a sense of incongruity in the steered state. It may be determined.

  Note that, as described above, the torque steer depends on the physical or mechanical configuration of the vehicle. More specifically, for example, when the length of the drive shaft is unequal due to the engine being placed horizontally or the like. It is noticeable in such cases. In such a case, the direction in which the steering wheel by torque steer is operated in advance can be specified as either the left or right, so that in the acceleration state that may cause torque steer, prior to the actual torque steer occurrence By applying the convergence steering force in a predetermined direction, it is possible to substantially avoid the occurrence of torque steer itself.

  In one aspect of the vehicle control apparatus according to the present invention, the auxiliary steering force applying means includes an electric motor.

  According to this aspect, since the auxiliary steering force applying means includes an electric motor such as a motor, for example, it is possible to apply the convergent steering force relatively easily and accurately. In this aspect, for example, the electric motor is configured as a part of the steering device, and is configured to be able to apply an assist torque that assists the rotation of the steering shaft, the rotation of the pinion gear, the reciprocation of the rack bar, or the like as the auxiliary steering force. It may be. That is, in this case, the steering device takes the form of a so-called EPS.

  In addition, the form of the electric motor in this aspect is not limited at all, and various forms such as a DC motor and a three-phase AC motor can be employed. Further, the power supply device that supplies electric power to the electric motor is not limited in any way. For example, the vehicle 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. The battery may be a 12V battery for the purpose, or may be a dedicated battery configured independently of such an auxiliary battery. Furthermore, a battery capable of supplying a relatively high secondary voltage by appropriately boosting the voltage supplied from these various batteries may be used.

  In another aspect of the vehicle control apparatus according to the present invention, the control means controls the auxiliary steering force applying means so that the convergent steering force is applied according to a steering angle of the steering wheel.

  According to this aspect, the convergence steering force is applied according to the steering angle of the steering wheel detected by the detection means such as a steering angle sensor. The convergent steering force is given for the purpose of canceling the torque steer and finally improving the running performance and comfort of the vehicle. From this viewpoint, the steering angle has an important meaning. That is, when the steering wheel is in the let-off state, it is preferable to suppress the steering wheel operation itself by torque steer, and it is desirable that the application of the convergent steering force is started from a relatively small steering angle. On the other hand, in a state where the driver holds the steering wheel at least, it is necessary to apply a convergent steering force according to the driver's intention to operate, so a constant or indefinite dead zone region is set for the steering angle. It may be better. According to this aspect, since the convergent steering force is applied according to the steering angle, for example, it is possible to appropriately meet such a request that can vary depending on the operation state of the steering wheel, which is useful in practice. is there.

  In this aspect, the control means provides the auxiliary steering force applying means so that the convergent steering force is applied based on a basic characteristic of the convergent steering force set in advance in association with the steering angle. May be controlled.

  In this case, for example, based on experimental, empirical, theoretical or simulation in advance, it is possible to suitably cancel the torque steer without causing the driver to feel uncomfortable regardless of the operation state of the steering wheel. As described above, the basic characteristic of the convergence steering force is determined, and is stored as a map or the like in an appropriate storage means, for example. Accordingly, the control means, when controlling the actual auxiliary steering force applying means, performs correction according to the index value such as the vehicle speed and the driving torque as appropriate based on the basic characteristics, and under a relatively light processing load. Thus, the convergent steering force can be suitably applied. Note that “based on the basic characteristics” means that the convergent steering force to be applied is not necessarily determined only according to the basic characteristics. More specifically, for example, as described above, the vehicle speed or This is intended to indicate that correction according to drive torque or the like may be performed.

  In a mode in which a convergent steering force is applied based on a basic characteristic, the control means has a first characteristic set as at least a part of the basic characteristic when the steering wheel is artificially operated. And (i) the maximum convergence steering force is set as at least a part of the basic characteristics when the auxiliary steering force applying means is controlled based on A value greater than the maximum value in the first characteristic, and (ii) a start steering angle representing the steering angle at which application of the convergent steering force is started is smaller than the start steering angle in the first characteristic The auxiliary steering force applying means may be controlled based on the second characteristic.

  In this case, when the steering wheel is artificially operated, that is, at least in the steering holding state, the auxiliary steering force applying means is controlled based on the predetermined first characteristic, and the steering wheel is artificially operated. When not being operated, i.e., in the let-off state, the maximum value is greater than the maximum value in the first characteristic with the steering angle being smaller than the start steering angle in the first characteristic according to the second characteristic. A large convergent steering force is applied. Therefore, it is possible to make the giving characteristic of the convergent steering force completely independent between the case where the steering wheel is in the let-off state and the state where the steering wheel is held, and the convergent steering force optimized in each case. Can be granted. Further, a map corresponding to the first and second characteristics, for example, a control amount (current value, torque value, duty ratio, etc.) of the auxiliary steering force applying means for obtaining the characteristics corresponding to the first and second characteristics. ) Is stored in an appropriate storage unit, as described above, the load on the control unit can be reduced, which is useful in practice.

  In the aspect in which the basic characteristic is switched at least between the first characteristic and the second characteristic in this way, the control means is configured to switch the basic characteristic between the first characteristic and the second characteristic. The auxiliary steering force applying means may be controlled so that the convergent steering force gradually changes.

  In many cases, there is a large difference in the value of the convergent steering force that cannot be ignored in practice between the hand-off state and the steered state. Accordingly, when the basic characteristics are switched during the torque steer generation or during the control for suppressing the torque steer, due to the change in the steering wheel operation state from the hand-off state to the steered state, for example, The driver may be given an uncomfortable feeling such as torque shock. In this aspect, since the control means gradually changes the convergent steering force when the basic characteristics are switched, such torque shock can be reduced at least to the extent that it is not perceived by the driver, which is beneficial in practice.

  Note that such a mode of gradual change is not limited in any way as long as it can suppress the occurrence of a sense of incongruity as much as compared with the case where this kind of control is not performed, and the convergence determined based on one characteristic. The convergence steering force may be changed continuously or stepwise from the steering force to the convergence steering force determined based on the other characteristic. Further, the period for executing the gradual change control of the convergent steering force at the time of such switching is not limited in any way as long as the running stability and comfort can be sufficiently secured, or from the time when the operation state changes or the operation It may be specified as a fixed or indefinite time from the time when some determination operation indicating that the state has changed is made. Regardless of the elapsed time, the difference in convergent steering force before and after switching and the degree of gradual change Depending on the time period, it may be a specific period of time.

  In the aspect in which the convergent steering force is gradually changed in this way, the control means is configured so that the convergent steering force when switching the basic characteristic is at least one time of the steering angle and the steering torque of the steering wheel. You may control the said auxiliary | assistant steering force provision means so that it may be provided based on a differential value.

  The time differential value of the steering angle, that is, the steering angular velocity and the time differential value of the steering torque can be an index that defines the degree of operation of the steering wheel by the driver. Therefore, when the convergence steering force at the time of switching the basic characteristics is given based on these index values, the uncomfortable feeling given to the driver is extremely reduced, and it is possible to provide the driver with a natural feeling of operation. Become. In addition, the convergence steering force at the time of basic characteristic switching given based on such an index value is when the driver cuts the steering wheel, that is, when the steering wheel is operated in a direction away from the neutral position. Of course, they may be different from each other when they are switched back, that is, when the steering wheel is returned to the neutral direction by the driver's intention.

  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 pair of left and right front wheels FL and FR as steering wheels, and is configured to be able to travel in a desired direction by steering these front wheels.

  The vehicle 10 includes an ECU 100, an EPS 200, and an engine 300.

  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 torque steer suppression processing to be described later for controlling the EPS 200 in accordance with a control program stored in the ROM.

  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 steering wheels, according to the operation of the steering wheel 11 by the driver.

  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 another steering method such as a ball nut type.

  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 detects the steering torque MT applied to the steering shaft 12 through the operation of the steering angle sensor 15 and the steering wheel 11 that are configured to detect the steering angle δ that is the rotation angle of the steering wheel 11. A torque sensor 16 configured to be able to do so is provided. The steering angle sensor 15 and the torque sensor 16 are electrically connected to the ECU 100, respectively, and the detected steering angle δ and steering torque MT are detected by the ECU 100 continuously or at regular or indefinite periods. It has become.

  The EPS 200 is provided with a motor 17. The motor 17 is configured to generate assist torque as an auxiliary steering force that reduces the operation burden on the driver and to apply the assist torque to the steering shaft 12 via a reduction gear (not shown). It is an example of the “auxiliary steering force applying means” according to the invention. The motor 17 is electrically connected to the ECU 100 via a motor control system (not shown) including, for example, an inverter, and the operation state is controlled by the ECU 100. The assist torque output from the motor 17 does not necessarily have to be applied to the steering shaft 12. For example, the assist torque output from the motor 17 may be applied to the pinion gear in the rack and pinion mechanism 13 to assist the rotation of the pinion gear. The rack bar 14 may be provided to assist the reciprocating motion of the rack bar.

  The vehicle 10 includes a front / rear G sensor 18, a vehicle speed sensor 19, and a throttle opening sensor 20.

  The front-rear G sensor 18 is a sensor configured to be able to detect acceleration (that is, front-rear G) Gx acting in the front-rear direction of the vehicle 10. The front-rear G sensor 18 is electrically connected to the ECU 100, and the detected front-rear G of the vehicle 10 is grasped by the ECU 100 constantly or at regular or indefinite periods.

  The vehicle speed sensor 19 is a sensor configured to be able to detect the speed (that is, the vehicle speed) V of the vehicle 10. The vehicle speed sensor 19 is electrically connected to the ECU 100, and the detected vehicle speed is grasped by the ECU 100 constantly or at regular or indefinite periods.

  The throttle opening sensor 20 is a sensor configured to detect a throttle valve opening (that is, a throttle opening) Thr in the engine 300. The throttle opening sensor 20 is electrically connected to the ECU 100, and the detected throttle opening is configured to be grasped by the ECU 100 constantly or at regular or indefinite periods.

  The engine 300 is an internal combustion engine configured to function as a power source of the vehicle 10 using gasoline as fuel, and includes, for example, a plurality of cylinders such as a 4-cylinder, a 6-cylinder, an 8-cylinder, and a 12-cylinder. Various types such as an in-line type, a V type, and a horizontally opposed type are adopted according to the arrangement mode of the cylinders. The driving force output from the crankshaft (not shown) in the engine 300 is applied to the front wheels FL and FR, which are the steering wheels, through a differential and a driveshaft (not shown) as appropriate. That is, the vehicle 10 is configured as an FF vehicle. Needless to say, the driving mode of the vehicle 10 is not limited to FF, and for example, a four-wheel driving mode in which a rear wheel (not shown) is driven in addition to the front wheels FL and FR may be adopted.

<Operation of Embodiment>
Next, the operation of this embodiment will be described.

  As described above, the vehicle 10 is an FF vehicle, and the front wheels FL and FR are steering wheels and driving wheels. For this reason, these front wheels are steered regardless of the driver's steering operation when a relatively large longitudinal acceleration occurs during a sudden start or the like, and so-called torque steer may occur. When torque steer occurs, there is a possibility that the driving performance may be lowered, and the steering force acting on the steered wheels is transmitted to the steering wheel 11 via the steering shaft 12, so that the driver's intention to steer is eventually obtained. The steering wheel 11 is operated regardless of the driver's feeling, and the driver is remarkably uncomfortable, so that the comfort is easily lowered. Therefore, in the vehicle 10 according to the present embodiment, the ECU 100 can suitably cope with the occurrence of such torque steer by executing the torque steer suppression process. Hereinafter, the torque steer suppression process will be described in detail with reference to the drawings as appropriate.

  First, the basic flow of torque steer suppression processing will be described with reference to FIG. FIG. 2 is a flowchart of the torque steer suppression process.

  In FIG. 2, the ECU 100 first determines whether or not the vehicle 10 is accelerating (step S100). Note that the determination as to whether or not the vehicle is accelerating is performed based on the result of the acceleration determination process.

  Here, the details of the acceleration determination process will be described with reference to FIG. FIG. 3 is a flowchart of the acceleration determination process.

  In FIG. 3, the ECU 100 determines whether or not the vehicle speed V detected by the vehicle speed sensor 19 is equal to or higher than a predetermined threshold value Vth (step S110). Here, the threshold value Vth of the vehicle speed is set in an extremely low vehicle speed region near zero as long as the detection error of the vehicle speed does not cause a problem in practice. When the vehicle speed V is less than the threshold value Vth (step S110: NO), the ECU 100 determines that the vehicle 10 is not accelerating (that is, corresponding to the “NO” branch in step S100 of FIG. 2).

  When the vehicle speed V is equal to or higher than the threshold value Vth (step S110: YES), the ECU 100 determines whether or not the throttle opening degree Thr detected by the throttle opening degree sensor 20 is equal to or higher than a predetermined threshold value Thrth (step S120). ). Here, the threshold value Thrth of the throttle opening is set in advance to a value associated with the occurrence of torque steer experimentally, empirically, theoretically, or based on simulation or the like. For example, the threshold Thrth is set to a value that can be estimated that the probability of occurrence of torque steer is relatively high. When the throttle opening degree Thr is less than the threshold value Thrth (step S120: NO), the ECU 100 determines that the vehicle 10 is not accelerating (that is, corresponding to the “NO” branch in step S100 of FIG. 2).

  When the throttle opening degree Thr is equal to or greater than the threshold value Thrth (step S120: YES), the ECU 100 further determines whether the longitudinal acceleration Gx of the vehicle 10 detected by the longitudinal G sensor 19 of the vehicle 10 is equal to or greater than a predetermined threshold value Gxth. Is determined (step S130). Here, the threshold value Gxth of the front and rear G is set in advance to a value associated with the occurrence of torque steer experimentally, empirically, theoretically, or based on simulation or the like. For example, the threshold value Gxth is set to a value that can be estimated that the probability of occurrence of torque steer is relatively high. When the longitudinal acceleration Gx is less than the threshold Gxth (step S130: NO), the ECU 100 determines that the vehicle 10 is not accelerating (that is, corresponding to the “NO” branch in step S100 of FIG. 2).

  When the longitudinal acceleration Gx is greater than or equal to the threshold Gxth (step S130: YES), the ECU 100 further determines whether or not the drive torque Drtrq of the vehicle 10 is greater than or equal to a predetermined threshold Drtrqth (step S140). Here, the drive torque Drtrq is a torque that actually drives the front wheels FL and FR, and is calculated by the ECU 100 based on the output torque of the engine 300, the differential gear ratio, and the like. The threshold value Drtrqth of the drive torque Drtrq is set in advance to a value associated with the occurrence of torque steer experimentally, empirically, theoretically, or based on simulation. For example, the threshold Drtrqth is set to a value that can be estimated that the probability of occurrence of torque steer is relatively high. If the drive torque Drtrq is less than the threshold Drtrqth (step S140: NO), the ECU 100 determines that the vehicle 10 is not accelerating (ie, corresponds to the “NO” branch in step S100 of FIG. 2).

  When the drive torque Drtrq is equal to or greater than the threshold Drtrqth (step S140: YES), the ECU 100 determines that the vehicle 10 is accelerating (that is, corresponding to the “YES” branch in step S100 of FIG. 2). Thus, in the acceleration determination process, it is determined whether or not the vehicle 10 is accelerating based on the values of the vehicle speed V, the throttle opening degree Thr, the longitudinal acceleration Gx, and the drive torque Drtrq. . When it is determined whether or not the vehicle 10 is in an acceleration state, the acceleration determination process ends.

  Returning to FIG. 2, when it is determined that the vehicle 10 is not accelerating (step S100: NO), the ECU 100 repeatedly executes step S100, and substantially controls the process to a standby state. On the other hand, when it is determined that the vehicle 10 is accelerating (step S100: YES), the ECU 100 further determines whether or not the steering wheel 11 is in the let-away state (step S200). Note that the determination as to whether or not the steering wheel 11 is in the released state is made based on the result of the released hand determination process.

  Here, with reference to FIG. 4, details of the let go determination process will be described. FIG. 4 is a flowchart of the hand release determination process.

  In FIG. 4, the ECU 100 determines whether or not the absolute value of the steering torque MT detected by the torque sensor 16 is less than a predetermined threshold value MTth1 (step S210). Here, since the steering torque MT can take either positive or negative values depending on the steering direction of the driver, an absolute value is referred to. The threshold value MTth1 is a value that can be estimated, for example, experimentally, empirically, theoretically, or based on a simulation in advance, for example, that the steering wheel 11 is in the let-off state, or that there is no steering input by the driver. (For example, a value that cannot be taken when there is a steering input by the driver). When the absolute value of the steering torque MT is equal to or greater than the threshold value MTth1 (step S210: NO), the ECU 100 indicates that the steering wheel 11 is not released (that is, the driver at least holds the steering wheel 11). (I.e., corresponding to the “NO” branch in step S200 of FIG. 2).

  When the absolute value of the steering torque MT is less than the threshold value MTth1 (step S210: YES), the ECU 100 determines whether or not the absolute value of the steering angular velocity ω of the steering wheel 11 is equal to or greater than a predetermined threshold value ωth1 (step). S220). Here, the steering angular velocity ω is a time differential value of the steering angle δ detected by the steering angle sensor 15 and is an index value that defines the operation speed when the steering wheel 11 is operated. Since the steering angle δ can take either a positive or negative value depending on the rotation direction of the steering wheel 11, the steering angular velocity ω can necessarily take either a positive or negative value. For this reason, the absolute value is referred to in the determination processing according to step S220. The threshold value ωth1 is set to a value that can be estimated that the steering wheel 11 is operated in any direction, whether artificially or by torque steer. When the absolute value of the steering angular velocity ω is less than the threshold value ωth1 (step S220: NO), the ECU 100 determines that the steering wheel 11 is not in the released state (that is, the branch of “NO” in step S200 of FIG. 2). Equivalent).

  When the steering angular velocity ω is greater than or equal to the threshold ωth1 (step S220: YES), the ECU 100 determines whether or not the absolute value of the steering angle δ of the steering wheel 11 detected by the steering angle sensor 15 is greater than or equal to a predetermined threshold δth1. It discriminate | determines (step S230). Here, as described above, since the steering angle δ can take either positive or negative values, an absolute value is referred to. Further, the threshold value δth1 is set to a value that can be estimated that the steering wheel 11 is operated in any direction, whether artificially or by torque steer. When the absolute value of the steering angle δ is less than the threshold value δth1 (step S230: NO), the ECU 100 determines that the steering wheel 11 is not in the released state (that is, the branch of “NO” in step S200 of FIG. 2). Equivalent). In the process according to step S230, it is simultaneously determined whether or not the sign of the steering angle δ matches the sign of the steering angular velocity ω.

  In the present embodiment, the absolute values of the steering angular velocity ω and the steering angle δ are referred to in the processing related to step S220 and step S230 as described above, but of course, the operation direction of the steering wheel 11 (ie, left and right) Two threshold values set for each direction), which are different only in sign, and steering angular velocity ω and steering angle δ may be individually compared and determined.

  When the absolute value of the steering angle δ is greater than or equal to δth (step S230: YES), the ECU 100 determines that the steering wheel 11 is in the hand-off state (that is, branches to “YES” in step S200 of FIG. 2). Equivalent). As described above, the hand release determination process is configured to determine whether or not the steering wheel 11 is in the hand release state based on the steering torque MT, the steering angular velocity ω, and the steering angle δ. Qualitatively, when the steering torque MT is sufficiently small and the steering angular velocity ω and the steering angle δ have the same sign and a certain value, the steering wheel 11 is in a state of letting it go. Is determined. When it is determined whether or not the steering wheel 11 is in the let-away state, the hand-release determining process ends.

  Returning to FIG. 2, when the steering wheel 11 is in the released state (step S <b> 200: YES), the ECU 100 executes the hand-released N return control for moving the steering wheel 11 to the neutral position (step S <b> 10). On the other hand, when the steering wheel 11 is not in the let-away state (step S200: NO), the ECU 100 determines whether or not to execute a steering N return control described later for assisting the driver in returning the steering wheel 11 to the neutral position. (Step S300). The determination as to whether or not execution is possible is performed based on the result of the permission determination process.

  Here, the details of the permission determination process will be described with reference to FIG. FIG. 5 is a flowchart of the permission determination process.

  In FIG. 5, the ECU 100 determines whether or not the absolute value of the steering torque MT is equal to or greater than a predetermined threshold value MTth2 (step S310). Here, the threshold value MTth <b> 2 is set to a value larger than the threshold value MTth <b> 1 related to determination of the hand-off state in order to clarify that the driver has an intention to steer the steering wheel 11. When the absolute value of the steering torque MT is less than the threshold value MTth2 (step S310: NO), the ECU 100 determines that the steering N return control is prohibited (that is, the branch of “NO” in step S300 of FIG. 2). Equivalent).

  On the other hand, when the absolute value of the steering torque MT is equal to or greater than the threshold value MTth2 (step S310: YES), the ECU 100 determines whether or not the absolute value of the steering angular velocity ω is equal to or greater than a predetermined threshold value ωth2 (step S320). Here, the threshold value ωth2 is set to a value larger than the threshold value ωth1 for determining the hand-off state. When the absolute value of the steering angular velocity ω is less than the threshold value ωth2 (step S320: NO), the ECU 100 determines that the steering N return control is prohibited (that is, the branch of “NO” in step S300 of FIG. 2). Equivalent).

  On the other hand, when the absolute value of the steering angular velocity ω is greater than or equal to the threshold ωth2 (step S320: YES), the ECU 100 determines whether or not the absolute value of the steering angle δ is greater than or equal to a predetermined threshold δth2 (step S330). Here, the threshold value δth2 is set to a value larger than the threshold value δth1 for determining the hand-off state. When the absolute value of the steering angle δ is less than the threshold value δth2 (step S330: NO), the ECU 100 determines that the steering N return control is prohibited (that is, the branch of “NO” in step S300 of FIG. 2). Equivalent).

  On the other hand, if the absolute value of the steering angle δ is greater than or equal to the threshold δth2 (step S330: YES), the ECU 100 determines that the N return control during steering is permitted (ie, “YES” in step S300 of FIG. 2). Equivalent to the branch). As described above, in the permission determination process, it is determined whether or not the execution of the steering N return control is permitted based on the steering torque MT, the steering angular velocity ω, and the steering angle δ.

  Returning to FIG. 2, when the N return control at the time of steering is not permitted (step S300: NO), the ECU 100 returns the process to step S100 and performs a series of processes following the determination process of whether or not the vehicle 10 is accelerating. Execute. On the other hand, when the steering N return control is permitted (step S300: YES), the ECU 100 executes the steering N return control (step S11). When the steering N return control is executed, the process returns to step S100, and a series of processes is repeated.

  Here, the details of the N return control at hand release will be described. When hand release N return control is executed, ECU 100 calculates hand release assist torque ATRQ1 (hereinafter referred to as “assist torque ATRQ1” as appropriate) to be output from motor 17, and the assist torque ATRQ1 is output. The control system of the motor 17 is controlled. The assist torque ATRQ1 is calculated according to the following equation (1).

ATRQ1 = ATRQ1base × GN1 × GN2 (1)
Here, ATRQ1base is a basic value of the assist torque ATRQ1, and GN1 and GN2 are gains for correcting the basic value ATRQ1base of the assist torque ATRQ1, respectively.

  Here, details of ATRQ1base, GN1, and GN2 will be described with reference to FIG. FIG. 6 is a schematic diagram conceptually showing the characteristics of ATRQ1base, GN1 and GN2.

  In FIG. 6, the characteristics of ATRQ1base (FIG. 6 (a)), the characteristics of gain GN1 (FIG. 6 (b)), and the characteristics of gain GN2 (FIG. 6 (c)) are shown from the upper stage to the lower stage.

  FIG. 6A is an example of the “second characteristic” according to the present invention. In FIG. 6A, the basic value ATRQ1base of the assist torque ATRQ1 is set in association with the steering angle δ, and its locus Is PRF_ATRQ1base shown in the figure. That is, the basic value ATRQ1base is small enough to be regarded as almost zero, and the steering angle range from the illustrated steering angle δ1 (that is, an example of the “starting steering angle” according to the present invention) to the steering angle δ2 (δ2> δ1). Set by. The maximum value is ATRQ1basemax. The maximum value ATRQ1basemax is set to a value of about 4 to 5 N · m.

  In FIG. 6B, the gain GN1 is a characteristic of the gain GN with respect to the driving torque Drtrq of the vehicle 10, and its locus is represented by the illustrated PRF_GN1. That is, the gain GN1 is set in a range equal to or greater than the drive torque Drtrq1 (at least the value of the above-mentioned Drtrqth), increases linearly in a range from Drtrq1 to Drtrq2 (Drrtrq2> Drrtrq1), and has a maximum value GN1max in Drtrq2. (For example, 1).

  In FIG. 6C, the gain GN2 is a characteristic of the gain GN with respect to the vehicle V, and the locus thereof is represented by the illustrated PRF_GN2. That is, the gain GN2 is set in the range of Vmax (Vmax> V1) above the vehicle speed V1 (at least a value equal to or greater than Vth described above), which is an extremely low vehicle speed, and is the maximum in the range from V1 to V2 (V2> V1). A value GN2max (for example, 1) is taken and set so as to decrease linearly within a range of V2 or more. According to these characteristics, the assist torque ATRQ1 calculated according to the above equation (1) takes a value approximately in the vicinity of ATRQ1basemax as the maximum value, and is a value that is corrected according to the drive torque Drtrq and the vehicle speed V.

  Next, details of the steering N return control will be described. When the steering N return control is executed, the ECU 100 calculates the steering assist torque ATRQ2 (hereinafter referred to as “assist torque ATRQ2” as appropriate) to be output from the motor 17, and the assist torque ATRQ2 is output. The control system of the motor 17 is controlled. The assist torque ATRQ2 is calculated according to the following equation (2).

ATRQ2 = ATRQ2base × GN1 × GN2 (2)
Here, ATRQ2base is a basic value of the assist torque ATRQ2, and GN1 and GN2 are gains for correcting the basic value ATRQ2base of the assist torque ATRQ2, respectively.

  Here, details of ATRQ2base, GN1, and GN2 will be described with reference to FIG. FIG. 7 is a schematic diagram conceptually showing the characteristics of ATRQ2base, GN1, and GN2. In the figure, the same reference numerals are given to the same parts as those in FIG. 6, and the description thereof will be omitted as appropriate.

  In FIG. 7, the characteristics of ATRQ2base (FIG. 7 (a)), the characteristics of gain GN1 (FIG. 7 (b)), and the characteristics of gain GN2 (FIG. 7 (c)) are shown from the upper stage to the lower stage. As is clear from FIG. 7, the characteristics of the gain GN1 (FIG. 7 (b)) and the characteristics of the gain GN2 (FIG. 7 (c)) are the same as those in FIG. 6, that is, the characteristics by PRF_GN1 and PRF_GN2, respectively. Is represented.

  On the other hand, FIG. 7A shows a characteristic of the basic value ATRQ2base of the assist torque ATRQ2, which is an example of the “first characteristic” of the present invention. In FIG. 7A, the basic value ATRQ1base of the assist torque ATRQ2 is set in association with the steering angle δ, and the locus thereof becomes the illustrated PRF_ATRQ2base. That is, the basic value ATRQ2base has a larger dead band than the basic value ATRQ1base shown in FIG. 6A, and the illustrated steering angle δ3 (δ3> δ1 is satisfied, that is, δ3 is related to the present invention. It is set in a steering angle range from “another example of“ starting steering angle ”) to a steering angle δ4 (δ4> δ3). The maximum value is ATRQ2basemax. The maximum value ATRQ2basemax is set to a value of about 0.3 to 0.4 N · m, and is set sufficiently smaller than the basic value ATRQ1base of the assist torque ATRQ1.

  As a result of outputting the assist torque ATRQ1 from the motor 17 in accordance with the above-described equation (1), when hand-release N return control is executed, a relatively large assist torque ATRQ1 is output from an extremely small steering angle, and steering is performed by torque steer. When the wheel 11 is operated, the steering wheel 11 is quickly returned to the neutral position. Or generation | occurrence | production itself of a torque steer is suppressed and the situation where the steering wheel 11 is operated contrary to a driver | operator's intention is prevented. That is, at the time of sudden acceleration in the released state, the steering wheel 11 is fixed at the neutral position or near the neutral position. Therefore, even when torque steer occurs, the running performance of the vehicle 10 does not decrease and the comfort does not decrease.

  In the present embodiment, when the release assist torque ATRQ1 is output, the base characteristic of the EPS 200 is switched, and the release release assist torque ATRQ1 is more effectively applied. At this time, the ECU 100 switches the base characteristic by executing the inertia compensation control and the viscosity compensation control of the EPS 200. That is, when the base characteristic is switched, the ECU 100 decreases the inertia of the steering wheel 11 (so-called steering inertia) and then increases the damping amount to increase the viscosity. By switching the base characteristics by such viscosity compensation and inertia compensation, the behavior of the steering wheel 11 can be effectively controlled by the hand-off assist torque ATRQ1.

  On the other hand, when the steering torque N return control is executed as a result of the output of the assist torque ATRQ2 from the motor 17 in accordance with the above-described equation (2), the steering wheel 11 has a larger dead zone effect than the hand-release N return control. This eliminates the feeling that the operation of the vehicle is excessively assisted and allows the driver to release the steering torque and compensate for a larger steering angle range than during N-return control. However, it becomes possible to improve the driving performance.

  Here, the N return control at the time of hand release and the N return control at the time of steering are greatly different in imparting characteristics such as the maximum value and the steering angle range, and therefore, any countermeasure is taken when switching from one control to the other control. If not, the driver may perceive the switching of the control as a torque shock and the comfort may be greatly reduced. Such a decrease in comfort is more likely to occur when switching from the hand-released N return control to the steering-time N return control than when switching from the steering-time N return control to the hand-released N return control. Therefore, in the torque steer suppression process, the torque shock is reduced when the control is switched from the hand-released N return control to the steering N return control, and the maintenance of comfort is realized.

  That is, returning to FIG. 2, when the N release return control is executed, the ECU 100 determines whether or not a steering input is made by the driver (step S400). Such a determination is made based on the result of the steering input determination process. Here, the details of the steering input determination process will be described with reference to FIG. FIG. 8 is a flowchart of the steering input determination process.

  In FIG. 8, the ECU 100 determines whether or not the absolute value of the steering torque MT is equal to or greater than a predetermined threshold value MTth3 (step S410). Here, the threshold value MTth3 is set to a value that is at least larger than the threshold value MTth1 related to the determination of the hand-off state, in view of the switching from the hand-off N return control. In the present embodiment, the threshold value MTth3 is set to a value larger than the threshold value MTth2 at which the execution of the steering N return control is permitted. If the absolute value of the steering torque MT is less than the threshold value MTth3 (step S410: NO), the ECU 100 determines that there is no steering input (ie, corresponds to the “NO” branch in step S400 of FIG. 2).

  On the other hand, when the absolute value of the steering torque MT is greater than or equal to the threshold MTth3 (step S410: YES), the ECU 100 determines whether or not the absolute value of the steering angular velocity ω is greater than or equal to a predetermined threshold ωth3 (step S420). Here, the threshold value ωth3 is set to a value larger than the threshold value ωth2 in which the execution of the steering N return control is permitted. When the absolute value of the steering angular velocity ω is less than the threshold value ωth3 (step S420: NO), the ECU 100 determines that there is no steering input (ie, corresponds to the “NO” branch in step S400 of FIG. 2).

  On the other hand, when the absolute value of the steering angular velocity ω is greater than or equal to the threshold ωth3 (step S420: YES), the ECU 100 determines whether or not the absolute value of the steering angle δ is greater than or equal to a predetermined threshold δth3 (step S430). Here, the threshold value δth3 is set to a value larger than the threshold value δth3 at which the execution of the steering N return control is permitted. If the absolute value of the steering angle δ is less than the threshold value δth3 (step S430: NO), the ECU 100 determines that there is no steering input (ie, corresponds to the “NO” branch in step S400 of FIG. 2).

  On the other hand, when the absolute value of the steering angle δ is equal to or greater than the threshold value δth3 (step S430: YES), the ECU 100 determines that there is a steering input (ie, corresponds to the “YES” branch in step S400 in FIG. 2). . As described above, in the steering input determination process, the determination regarding the presence or absence of the steering input by the driver is performed based on the steering torque MT, the steering angular velocity ω, and the steering angle δ.

  Returning to FIG. 2, if it is determined that the steering input is not made (step S400: NO), the ECU 100 returns the process to step S100, and also indicates that the steering input has been made during the release-time N return control. Is determined (step S400: YES), it is determined whether or not the steering input corresponds to the cutting operation (step S12). Here, whether or not the steering input is a cutting operation is performed based on the steering torque MT, the steering angular velocity ω, and the steering angle δ, and when these index values have the same sign, the cutting operation is performed. It is configured to determine that an operation is being performed. On the other hand, when the steering torque MT, the steering angular velocity ω, and the steering angle δ have different signs, it is determined that the steering input by the driver is a switchback operation.

  When the steering input is a cutting operation (step S12: YES), the ECU 100 executes switching control at the time of cutting (step S13), and when the steering input is a switching operation (step S12: NO), at the time of switching back. Switching control is executed (step S14).

  In the switching control at the time of cutting, the ECU 100 calculates the switching assist torque ATRQ3 (hereinafter referred to as “assist torque ATRQ3” as appropriate) according to the following equation (3), and sets the control system of the motor 17 so that the ATRQ3 is output. Control.

ATRQ3 = GN3 × GN4 × ATRQ2 (3)
Here, GN3 and GN4 are gains for correcting the assist torque ATRQ2 in the above-described steering N return control. At this time, the assist torque ATRQ1 related to the N release return control is controlled to zero. That is, in the cutting operation, the steering wheel 11 is operated in the cutting direction by the driver's intention, and the assist torque ATRQ1 that invites the steering wheel 11 to the neutral position may give the driver a sense of incongruity.

  Here, the details of the gains GN3 and GN4 will be described with reference to FIG. FIG. 9 is a schematic diagram conceptually showing the characteristics of the gain GN3 and the gain GN4.

  In FIG. 9, the characteristics of the gain GN3 are shown in FIG. 9A, and the locus thereof is shown as PRF_GN3 in the drawing. That is, the gain GN3 is a gain associated with the steering angular velocity ω, increases linearly in the range from zero to ω1, and in the range where the steering angular velocity ω is larger than ω1, the maximum value GN3max ( It is fixed at a value of about 1). Note that the value of the steering angular velocity ω1 is, for example, experimentally, empirically, theoretically, or based on simulation in advance, and a sense of incongruity due to the assist torque ATRQ2 that is output in the opposite direction to the driver's steering operation. Is set to a value that can be avoided without causing it to become practically manifest by the driver's steering operation. Qualitatively, when the steering wheel 11 is operated slowly (corresponding to the case where the steering angular velocity ω is small), the assist torque is reduced by reducing the gain GN3 in view of the relatively high operation sensitivity of the driver. When ATRQ3 is controlled to decrease and the steering wheel 11 is operated quickly (corresponding to the case where the steering angular velocity ω is large), the gain GN3 is not reduced in view of the relatively low operation sensitivity of the driver, and the assist The torque ATRQ3 asymptotically approaches the assist torque ATRQ2. Further, the characteristic of the gain GN4 is shown in FIG. 9B, and the locus thereof is shown as PRF_GN4 in the drawing. That is, the gain GN4 is curvilinearly decreased from the maximum value (generally 1) as the steering torque differential value DMT increases.

  Thus, in the switching control at the time of turning, the assist torque ATRQ2 is corrected by the gains GN3 and GN4 determined based on the steering angular velocity ω and the steering torque differential value DMT, and the torque output from the motor 17 is gradually changed. Therefore, the occurrence of uncomfortable feeling at the time of control switching is suppressed.

  On the other hand, in the switching control at the time of switching back, the ECU 100 calculates the switching assist torque ATRQ4 (hereinafter referred to as “assist torque ATRQ4” as appropriate) according to the following equation (4), and outputs the ATRQ4 so that the ATRQ4 is output. Control the control system.

ATRQ4 = GN5 × ATRQ1 + ATRQ2 (4)
Here, GN5 is a gain for correcting the assist torque ATRQ1 in the above-described N release return control. Here, the details of the gain GN5 will be described with reference to FIG. FIG. 10 is a schematic diagram conceptually showing the characteristic of the gain GN5.

  In FIG. 10, the characteristic of the gain GN5 is shown as PRF_GN5 in the figure. That is, the gain GN5 is a gain associated with the steering angular velocity ω, and decreases in a curve from the maximum value (generally 1) as the steering angular velocity ω increases. Therefore, as the driver operates the steering wheel 11 faster, the assist torque ATRQ4 gradually approaches the steering assist torque ATRQ2, and the uncomfortable feeling given to the driver is reduced.

  As described above, in the switching control at the time of switching back, the assist torque ATRQ1 is corrected by the gain GN5 determined based on the steering angular velocity ω, and the torque output from the motor 17 is gradually changed. Is suppressed.

  In addition, the execution period of the switching control at the time of cutting and the switching control at the time of switching back is not limited at all. For example, based on experimental, empirical, theoretical, or simulation, the switching control is performed for a fixed or indefinite period that is adapted as a period sufficient to dispel the sense of incongruity at the time of control switching. Alternatively, the assist torque corresponding to the switching control is output only once during the time interval between the assist torque ATRQ1 output according to the N return control when released and the assist torque ATRQ2 output according to the N return control during steering. May be.

  Returning to FIG. 2, when the switching control at the time of cutting or the switching control at the time of switching back is performed, the ECU 100 returns the process to step S100 and repeats a series of processes. The torque steer suppression process according to the present embodiment is performed as described above. As described above, according to the torque steer suppression process according to the present embodiment, the return failure of the steering wheel 11 due to the torque steer is compensated regardless of whether the steering wheel 11 is in the hand-off state or the steered state. The running performance and comfort of the vehicle 10 are ensured. At this time, in particular, at the time of switching from the N release returning control to the steering N returning control, the assist torque output from the motor 17 is gradually changed based on the steering angular velocity ω or the steering torque differential value DMT, and the driving is performed at the switching. Occurrence of an uncomfortable feeling that can be given to the person is suppressed, and a natural steering feeling is realized. In other words, the steering wheel operation by torque steer can be effectively converged regardless of the steering state of the driver.

  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 of the torque steer suppression process in the vehicle of FIG. It is a flowchart which shows the operation | movement in step S100 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 S300 of FIG. It is a schematic diagram conceptually showing the characteristics of ATRQ1base, GN1 and GN2 in the process of calculating the release assist torque. FIG. 5 is a schematic diagram conceptually showing characteristics of ATRQ2base, GN1, and GN2 related to a calculation process of steering assist torque. It is a flowchart which shows the operation | movement in step S400 of FIG. It is a schematic diagram showing the characteristic of gain GN3 and GN4 at the time of cutting change control. It is a schematic diagram showing the characteristic of gain GN5 in switching control at the time of switching back.

Explanation of symbols

  FL, FR ... wheels, 10 ... vehicle, 100 ... ECU, 200 ... EPS, 11 ... steering wheel, 12 ... steering shaft, 13 ... rack and pinion mechanism, 15 ... rudder angle sensor, 16 ... torque sensor, 17 ... motor, 18: Front / rear G sensor, 19: Vehicle speed sensor, 20 ... Throttle opening sensor, 300 ... Engine.

Claims (7)

A vehicle control device for controlling a vehicle provided with auxiliary steering force applying means capable of applying an auxiliary steering force for assisting a steering force applied to a wheel via a steering wheel,
Discriminating means for discriminating whether or not the vehicle is in a predetermined acceleration state;
A specifying means for specifying an operation state of the steering wheel including at least a binary state of whether or not the steering wheel is artificially operated;
When it is determined that the vehicle is in the acceleration state, a predetermined convergent steering force that directs the steering wheel toward the neutral position as the auxiliary steering force with respect to the wheel based on the specified operation state And a control means for controlling the auxiliary steering force application means so that the vehicle is given. The vehicle control device according to claim 1, wherein the auxiliary steering force applying means includes an electric motor. 3. The vehicle control device according to claim 1, wherein the control unit controls the auxiliary steering force applying unit so that the convergent steering force is applied in accordance with a steering angle of the steering wheel. . The control means controls the auxiliary steering force applying means so that the convergent steering force is applied based on a basic characteristic of the convergent steering force set in advance in association with the steering angle. The vehicle control device according to claim 3. The control means controls the auxiliary steering force applying means based on a first characteristic set as at least a part of the basic characteristic when the steering wheel is artificially operated, and the steering When the wheel is not artificially operated, (i) the maximum value of the convergent steering force set as at least part of the basic characteristic is larger than the maximum value in the first characteristic, and ( ii) controlling the auxiliary steering force applying means based on a second characteristic in which a starting steering angle representing the steering angle at which the application of the convergent steering force is started is smaller than the starting steering angle in the first characteristic. The vehicle control device according to claim 4. The control means controls the auxiliary steering force applying means so that the convergent steering force gradually changes when the basic characteristic is switched between the first characteristic and the second characteristic. The vehicle control device according to claim 5. The control means provides the auxiliary steering force application means so that the convergent steering force when the basic characteristic is switched is applied based on a time differential value of at least one of the steering angle and the steering torque of the steering wheel. The vehicle control device according to claim 6, wherein:

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