JP2009185643A - Vehicle behavior control device - Google Patents

Abstract

In a vehicle behavior control apparatus that executes a drive output limitation of a vehicle when a turning state index value satisfies a predetermined condition, driving in the behavior control according to a condition different from the conventional behavior control The ability to release the output restriction or reduce the drive output restriction so that the vehicle can be accelerated quickly as intended by the driver.
A vehicle behavior control apparatus according to the present invention includes drive output limiting means for limiting drive output of a vehicle in order to avoid deterioration of behavior such as understeer, oversteer, spin, and driftout. Even if the turning state index value satisfies a predetermined condition, when the steering angle is less than the predetermined angle, the drive output limiting means releases at least a part of the limit of the drive output.
[Selection] Figure 2

Description

  The present invention relates to a vehicle behavior control device that stabilizes the behavior of a vehicle such as an automobile during travel, and more specifically, executes output limitation of a drive device such as an engine / motor according to the state quantity of the vehicle. Related to the device.

  In the field of motion control of vehicles such as automobiles, VSC (Vehicle Stability Control) which improves the stability of the behavior of the vehicle in the yaw direction while turning by electronically controlling the operation of the braking / driving system or steering system Many behavior control techniques have already been proposed. In a typical VSC, a turning state quantity representing the turning state of the vehicle is monitored, and when the vehicle behavior becomes oversteered or understeered, or when it is about to fall into a spin state or driftout state. The slip ratio of the tires on each wheel is adjusted, or the engine or motor output is reduced or restricted, and the acceleration of the vehicle is restricted. As is well known, when a braking / driving force difference is generated between the left and right wheels of a vehicle, a yaw moment is generated around the center of gravity of the vehicle, thereby changing the turning direction of the vehicle and reducing the vehicle speed. As a result, the lateral force required for turning will be reduced, so adjusting the slip ratio of each wheel and limiting or decelerating the acceleration of the vehicle will eliminate the oversteer or understeer condition and Stabilization will be achieved.

As described above, the behavior control as described above is generally performed by an arbitrary index value representing the state of the turning behavior of the vehicle, for example, the yaw rate, slip angle or predetermined state quantity (oversteering of the vehicle during turning). These values are assumed in a vehicle that is running stably with reference to the vehicle's current state, such as state quantity, understeer state quantity, spin state quantity, and drift state quantity. Automatically start adjusting the slip ratio of each wheel and / or limiting the drive output of the vehicle when the value range is out of the range or when the index value exceeds (or falls below) a predetermined threshold value. When the index value settles in the stable running range, each wheel slip ratio adjustment and / or drive output restriction is canceled and the process ends (see, for example, Patent Document 1). With regard to the end of such behavior control, in Patent Documents 2 and 3, particularly when the drive output restriction is executed, the output of the drive device is quickly adjusted so that the vehicle behavior does not become unstable again. In order to increase to a magnitude corresponding to the amount of depression, a control method has been proposed in which an increasing gradient of drive output is determined while referring to the magnitude of the friction coefficient of the road surface.
JP-A-2005-273584 JP-A-9-125999 JP 2003-184599 A

  As described above, the conventional behavior control of the VSC or the like as exemplified above has a stable turning state amount such as a yaw rate deviation (a difference between a target yaw rate determined based on a vehicle model and an actual yaw rate). It will continue until it is released after it settles within the range. Therefore, in the case of behavior control in which drive output is limited, even if the driver steps on the accelerator until the turning state amount is within the range of stable travel, the increase in drive output is suppressed compared to during normal travel. The vehicle is not accelerated as the driver thinks. Of course, the drive output limitation in the behavior control is a control for ensuring the driving stability of the vehicle by assisting the driver's maneuvering. When executed, the driver may rather feel uncomfortable that the vehicle is not accelerated as requested. In fact, an experienced driver with a high driving skill may be able to correct the vehicle behavior by the driver's own maneuvering even if the behavior control is canceled before the turning state quantity completely settles within the range of stable driving. is there. Therefore, for such a skilled driver, the drive output limitation based on the behavior control is limited to the conventional control mode under a condition different from the release condition of the previous behavior control (the amount of turning state settles within the stable travel range). It would be better to release the vehicle earlier or reduce the degree of the drive output restriction so that the vehicle can be accelerated as intended or perceived by the driver earlier.

  Thus, one object of the present invention is to provide a behavior control apparatus configured to release the drive output limit or reduce the degree of the drive output limit in the behavior control in accordance with conditions different from the conventional behavior control. It is to be.

  Further, another problem of the present invention is that it is possible to cancel the drive output restriction or reduce the degree of the drive output restriction at an early stage as compared with the conventional behavior control. It is another object of the present invention to provide a behavior control device that can accelerate quickly.

  According to the present invention, in short, in a vehicle behavior control device for avoiding an understeer state, an oversteer state, a spin or a drift-out of a running vehicle, based on a conventional turning state index value. The limit control of the vehicle drive output to be executed is canceled or the output limit is reduced by a condition different from the previous condition, and the drive output limited under the behavior control is compared to the previous condition. A behavior control device configured to be able to return more smoothly is provided.

  The vehicle behavior control device of the present invention includes drive output limiting means for limiting the drive output of the vehicle drive device when the turning state index value representing the turning state of the vehicle satisfies a predetermined condition. Even when the predetermined condition is satisfied, when the magnitude of the steering angle falls below the predetermined angle, the drive output restriction means releases at least a part of the restriction on the drive output. Here, the turning state index value is typically a steering angle, a vehicle speed, or the like used in various behavior control apparatuses known by the names of known VSC and VDIM (Vehicle Dynamical Integrated Management). A function value (referred to as an understeer state amount or an oversteer state amount) such as a deviation between a target yaw rate and an actual yaw rate determined based on the above, or a spin state amount calculated from a vehicle body slip angle, a drift out The behavior control device of the present invention may basically operate in the same manner as conventional VSC and VDIM. Therefore, the drive output limit for behavior control is typically determined based on the turning state index values as described above, that the index values deviate from a predetermined range, and the turning behavior of the vehicle has become unstable. It is executed in response to the event (when a predetermined condition is satisfied).

  However, in the behavior control device of the present invention, the limitation of the driving output executed by the driving output limiting means is that the magnitude of the steering angle is predetermined even if the turning state index value as described above satisfies a predetermined condition. When the angle falls below the angle, at least a part of the angle is released, and the increase in drive output can be made closer to the driver's request earlier regardless of the turning state index value as described above. As described above, in the case of the above-described conventional VSC and VDIM, the cancellation of the limit of the drive output or the end of the limit control responds to the fact that the turning state index value has settled within the predetermined range as described above. As long as the turning state index value deviates from a predetermined range, the drive output is limited. In that case, even if the driver depresses the accelerator to accelerate the vehicle according to the determination in consideration of the state of the vehicle according to his / her driving skill, the increase gradient of the vehicle speed is limited, and the driver may feel uncomfortable. Therefore, in the present invention, the drive output restriction control is canceled or the control action is reduced based on a reference different from the turning state index value. The behavior control is modified to follow.

  As one of the criteria for canceling the drive output restriction control or reducing the control action, which is different from the turning state index value, first, as described above, when the magnitude of the steering angle falls below a predetermined angle That is, it is adopted that the driver has returned the steering wheel of the turning vehicle and has been steered so that the vehicle is almost straight. In this case, since the vehicle is subsequently released from the turning state, the operation of the drive output restriction control is reduced without waiting for the turning state index value to settle within a predetermined range, thereby The vehicle will be smoothly accelerated.

  However, before the turning state index value settles within a predetermined range, the behavior of the vehicle itself is unstable, so depending on the skill of the driver, if the magnitude of the steering angle is less than the predetermined angle, In some cases, it is better to maintain the drive output limit. Therefore, in addition to the steering angle condition, one or both of the fact that the amount of understeer state in the turning state index value has decreased and the lateral acceleration of the vehicle is smaller than the predetermined acceleration or both are further limited to drive output. It may be a condition for reducing the action of control. Furthermore, even if the above conditions are met, the behavior is difficult to stabilize when the vehicle speed is high, so the drive output limit amount when the drive output limiting means releases at least a part of the drive output limit. May be determined based on the vehicle speed.

  In the behavior control device according to the present invention, if necessary, the vehicle output can be reduced as compared with the conventional device by increasing the opportunity to release the drive output limitation or reduce the control action during the behavior control. The acceleration of the vehicle is made as intended by the driver. In the first place, the behavior control of the vehicle is for assisting the driver's maneuvering so as to facilitate the driver's maneuvering of the vehicle, and the necessity for the assistance varies depending on the skill of the driver. In the present invention, it is possible to increase the diversity of the driver's steering support for the purpose of controlling the behavior of the vehicle by increasing the opportunity to release the drive output restriction or reduce the control action. it can. The behavior control device of the present invention is expected to provide a user-friendly control mode particularly in a circuit-driving vehicle in which a driver has a relatively high level of driving skill.

  Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention.

Diagram 1 of a vehicle is a motor vehicle in which the preferred embodiment of the behavior control device of the present invention is incorporated is shown schematically. In the figure, a vehicle 10 having left and right front wheels 12FL and 12FR and left and right rear wheels 12RL and 12RR is arranged in a normal manner according to the depression of the accelerator pedal 16 by the driver (in the example shown in the figure). A drive system 20 that generates braking / driving force on the rear wheels only, and a steering device 30 for controlling the steering angle of the front wheels (further, a steering device for the rear wheels is provided). And a braking system device (not shown) for generating a braking force on each wheel. The drive system device is configured so that drive torque or torque is transmitted from the engine and / or motor 22 to the rear wheels 12RL and 12RR via the transmission 26, the differential gear device 28, and the like in a normal manner. (It may be a front wheel drive vehicle or a four wheel drive vehicle.) Further, the steering device transmits the rotation of the steering wheel 32 operated by the driver to the tie rods 36L and 36R while boosting the rotational force by the booster 34, and steers the front wheels 12FL and 10FR. It may be. The braking system is controlled by an electronic control unit 50 so that each wheel is driven by a hydraulic circuit 46 (not shown) that communicates with a master cylinder that is operated in response to the driver depressing a brake pedal 44 (not shown). It may be an electronically controlled hydraulic brake device in which the brake pressure in the wheel cylinder equipped with, i.e., the braking force in each wheel is individually adjusted. The braking system device may be of a type that applies a braking force to each wheel pneumatically or electromagnetically, or any other type for those skilled in the art.

  The behavior control of the present invention and the operation control of the drive system device 20 and the brake system device are realized in the electronic control unit 50 as already mentioned. The electronic control unit 50 may include a microcomputer having a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other by a bidirectional common bus, and a driving circuit. In the figure, the electronic control unit 50 includes an accelerator pedal depression amount θa, a steering angle δ, a wheel speed Vwi from a wheel speed sensor 14i (i = FL, FR, RL, RR, and so on), a lateral G sensor. Although the detection values such as the lateral acceleration Gy from 62 and the yaw rate γ from the yaw rate sensor 64 are illustrated as input, various parameters necessary for various controls to be executed in the vehicle of this embodiment, For example, various detection signals such as front and rear G sensor values and pressure in the wheel cylinder of each wheel may be input.

Configuration and Operation of Behavior Control Device FIG. 2 shows the configuration of the behavior control device of the present invention realized by the electronic control device 50 in the form of a control block. It should be understood that the configuration and operation of the illustrated control device are realized by processing operations of the CPU and the like in the electronic control device 50 during operation of the vehicle.

  Referring to the figure, the control device for executing the behavior control of the present embodiment may be similar to any known type of VSC and VDIM device in its basic configuration. In this behavior control apparatus, generally speaking, when the VSC unit 50a detects that the vehicle has fallen into or is likely to fall into an understeer state, an oversteer state, a spin state, or a drift-out state, the braking system device To each of the braking control device 50b and the drive control device 50c that executes torque control of the engine or motor, respectively, the target slip ratio Si of each wheel and the torque reduction rate for the generated torque (drive output) of the drive device, The yaw moment is generated in the vehicle, or the vehicle speed is limited, thereby stabilizing the vehicle behavior. However, in the case of the control device of the present invention, regarding the drive output limitation due to the torque down rate with respect to the torque generated by the drive device during behavior control, when the steering angle δ is smaller than a predetermined angle, that is, the driver When the (steering wheel) is returned and the vehicle is going to travel straight ahead, a configuration is provided that releases at least a part of the drive output restriction (under the condition of the following expression (4)) (torque down rate) Release gain determination unit 50e). Thus, even when the behavior is being controlled, when the driver depresses the accelerator pedal after returning the steering wheel to a substantially central position, the vehicle is smoothly moved, that is, in a mode that conforms to the driver's intention. Can be accelerated.

Specifically, first, the VSC unit 50a, like the known VSC, controls the steering angle δ of the steering wheel rotated by the driver, the vehicle speed Vx, the actual yaw rate γ from the yaw rate sensor, or the actual yaw rate from the lateral G sensor. Reference is made to the lateral acceleration Gy. Here, the vehicle speed Vx may be determined in any known manner from the wheel speed value Vwi of each wheel from the wheel speed sensor (50d: when a vehicle speed sensor is provided, the detected value is used. Yes.) In the VSC unit 50a, as a turning state amount (turning state index value) representing the behavior of the vehicle during turning from the reference value,
Understeer state quantity: US = (γt−γ) × signδ (1a)
Oversteer state quantity: OS = (γ−γt) × signδ (1b)
Spin state quantity: SP = w1 · | Gy−γVx | + w2 · ∫ | Gy−γVx | dt (1c)
Are calculated respectively. Here, sign δ is a sign of steering angle ± 1. γt is a target yaw rate, and may be given from the steering angle δ and the vehicle speed Vx, for example, by the vehicle turning model as follows.
γt = Vx · δ / N · L-Gy · kh · Vx (2)
Here, N, L, and kh are a steering wheel gear angle ratio (δ / N is a front wheel steering angle), a wheel base, and a vehicle turning characteristic value (constant), respectively. Also, w1 and w2 in (1c) are weighting factors. The US state quantity and the OS state quantity are set to 0 when they are negative values. Exemplary US state quantities are often referred to as “drift-out state quantities”.

  In the above-mentioned turning state quantity, the US state quantity represents a state in which the actual yaw rate is below the target yaw rate (theoretically appropriate value), that is, the degree of the understeer state. The OS state quantity represents a state in which the actual yaw rate exceeds the target yaw rate, that is, the degree of the oversteer state. The SP state quantity is an index value of the side slip amount of the vehicle during turning, and corresponds to the magnitude of (stabilized) yaw moment necessary to return the side slip angle to zero. In the VSC unit 50a, first, the target value Si of the slip ratio (tire force) of each wheel tire for generating a yaw moment for correcting the turning behavior of the vehicle is determined so that all of these turning state quantities become zero. Is done. Then, the target slip ratio Si is transmitted to the brake control device 50b, and the brake control device 50b considers the amount of depression of the brake pedal 44 so that the target slip ratio Si of each wheel is achieved. A control command (commands for various valves and pumps in the circuit) is given to 46, and a braking device (wheel cylinder) for each wheel is operated. [Typically, instead of generating the yaw moment necessary and sufficient to correct the behavior, when the amount of turning state exceeds the respective threshold value, an appropriate amount is determined according to the magnitude of the amount of turning state. The slip ratio of each wheel is distributed and controlled in the direction in which the yaw moment is generated, and the slip ratio is adjusted by feedback control so that each turning state amount settles below a predetermined value. ]

Further, when the above-mentioned turning state amount is larger than 0, it is possible that the lateral force necessary for turning cannot be generated in the vehicle, or the tire force of the rear wheel may reach the limit. Furthermore, in order to limit the speed increase of the vehicle, the drive output is limited as described above (if the vehicle speed is reduced, the lateral force required for turning is reduced and the vehicle behavior is stabilized). Specifically, in the VSC section 50a, each of the turning state amounts calculated as described above is used as a variable. First, the torque down rate Td as already mentioned is a map illustrated in FIG. Is determined. The torque down rate Td has a value of 0 to 100, and is an amount that determines a reduction range of the required torque required for the drive device (engine or motor). In the drive control device 50c, the driver request torque T is determined based on the depression amount (accelerator opening) of the driver's accelerator pedal, and the drive device is determined from the driver request torque T and the torque down rate Td. The required drive torque Tf given to
Tf = T · (100−Td) / 100 (3)
Determined by. In addition, when giving the torque down rate Td from which US state quantity, OS state quantity, or SP state quantity differs simultaneously, the largest torque down rate Td may be selected. The demanded drive torque Tf thus determined is converted into a control command for each part of the drive device that realizes the value (the control command is a throttle opening degree or the like in the case of a gasoline engine) and is driven. It is given to each part of the device. Thus, as understood from the map of FIG. 3A and equation (3), while any of the turning state amounts gives a torque down rate Td greater than 0, basically, according to equation (3), The drive output of the drive device is limited.

  However, in the behavior control apparatus of the present invention, as described above, even when any of the turning state amounts gives a torque-down rate Td greater than 0 during behavior control, the driver can When the steering wheel is returned to travel straight ahead, the torque-down rate is reduced so that the vehicle can be smoothly accelerated in a manner according to the driver's intention. In order to achieve such an action, the torque down rate release gain determination unit 50e is provided in the apparatus of the present embodiment.

The torque down rate release gain determination unit 50e calculates a release gain Kg for reducing the action of the torque down rate Td determined by the VSC unit 50a under a predetermined condition. Specifically, the torque-down rate cancellation gain determination unit 50e determines whether the steering angle δ, the lateral acceleration Gy, and the US state in order to determine whether the steering wheel has been returned or whether the vehicle has been steered to travel straight ahead. With reference to the quantity, it may be determined whether or not all of the following conditions are satisfied.
| Δ | <δo (4a)
| Gy | <Gyo (4b)
ΔUS <0 (4c)
Here, the steering angle δ and the lateral acceleration Gy are both determined by absolute values, and δo and Gyo are predetermined values that may be determined experimentally or theoretically, respectively. ΔUS is a time change rate (or change amount for each control cycle) of the US state quantity. Note that, preferably, regarding the determination of the expression (4c), when the state where the above expression is satisfied continues for a predetermined time, it may be determined that each state is satisfied.

When all of the equations (4a) to (4c) are not satisfied, the release gain Kg is
Kg = 1
(Thus, the reduction of the torque down rate is not executed). On the other hand, when all of the equations (4a) to (4c) are satisfied regardless of the above-described turning state quantity, the vehicle speed Vx is used as a variable, and a release gain is obtained using a map as illustrated in FIG. Kg is determined. Then, the release gain determined in this way is given to the drive control device 50c, and the required drive torque Tf is not the expression (3) but the following expression: Tf = T · (100−Td · Kg) / 100 (5) )
Is converted into a control command and transmitted to the drive device.

  Of the above formulas (4a) to (4c), the formula (4a) corresponds to determining that the driver has returned the steering wheel so that the vehicle travels substantially straight. Thus, according to the above configuration, when the driver returns the steering wheel, Kg multiplied by the torque down rate Td in the equation (5) becomes less than 1, and the torque down amount is reduced. The drive output restriction set by is at least partially released, and the acceleration of the vehicle according to the accelerator depression amount is partially restored. In this regard, in general, if the steering wheel is returned toward the center position and the vehicle travels straight, then the behavior of the vehicle is stabilized. However, if the drive output restriction is canceled simply by returning the handle, the behavior may change in an unstable direction. Therefore, it is also determined whether or not the expression (4b) [not turning suddenly] and the expression (4c) [change in behavior to stabilize] are established together with the condition of the expression (4a). (However, the conditions of the formulas (4b) and (4c) are not essential). Also, since the behavior is difficult to stabilize when the vehicle speed is high, the release gain Kg is set to approach 1 as the vehicle speed increases, as understood from FIG. 3B. The output limit may be maintained.

  Thus, according to the above configuration, when the drive output restriction is executed as one of the behavior controls, the handle is returned to the vicinity of 0 even before the drive output restriction is released by the value of the turning state amount. When the vehicle is driven to travel straight ahead, if the driver desires (by stepping on the accelerator), the vehicle will be accelerated to a higher extent than during normal behavior control, Comfortable vehicle travel can be provided. When the required drive torque is determined by the above equation (5), the release gain Kg contributes to the determination of the required drive torque when the behavior control is executed and the torque down rate Td becomes greater than zero. Further, the release gain Kg is determined by a condition different from the turning state quantity. In other words, the present invention can be said to execute the release of the drive output restriction during execution of behavior control under a condition different from the previous one, or to propose a new option for releasing the drive output restriction.

  Further, the change in the release gain depending on the vehicle speed in FIG. 3B may be variously changed according to the use of the vehicle on which the behavior control device of the present invention is mounted. For example, in a circuit traveling vehicle, a racing car, or the like that is driven by a skilled driver, the value of the release gain may be reduced and the vehicle speed at which the release gain becomes 1 may be set higher.

  While the present invention has been described in detail with respect to one embodiment thereof, it will be apparent to those skilled in the art that various modifications can be made within the scope of the present invention.

  For example, in the present embodiment, the torque down rate, that is, the reduction range of the required torque is determined, and the required torque is reduced by the ratio, but in the VSC section, the gain ( (Equivalent to (1-Td) of Expression (3)) is determined, and when Expressions (4a) to (4c) are established, the gain may be increased. In addition, it should be understood that the behavior control mode and the turning state quantity are not limited to those illustrated, but may be of any type, and such are also within the scope of the present invention.

FIG. 1 is a schematic view of a vehicle on which a preferred embodiment of the behavior control device of the present invention is mounted. FIG. 2 is a control block diagram of an electronic control device that realizes a preferred embodiment of the behavior control device according to the present invention. FIG. 3A shows, in the form of a graph, maps for determining the torque reduction rate with reference to the turning state amounts US, OS, and SP in the VSC unit 50a. FIG. 3B shows a map in the form of a graph for determining the release gain Kg with reference to the vehicle speed Vx in the release gain determination unit. Either map may be determined experimentally or theoretically to fit an actual vehicle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Vehicle 14FL-RR ... Wheel speed sensor 22 ... Drive apparatus (engine or motor)
28 ... Differential gear 32 ... Steering wheel (handle)
34 ... Booster 50 ... Electronic controller 62 ... Lateral acceleration sensor 64 ... Yaw rate sensor

Claims (6)

  A vehicle behavior control device, comprising: a driving output limiting means for limiting a driving output of the driving device of the vehicle when a turning state index value representing a turning state of the vehicle satisfies a predetermined condition; Even if the index value satisfies the predetermined condition, the drive output limiting means releases at least a part of the limit of the drive output when the magnitude of the steering angle falls below the predetermined angle. apparatus.   2. The apparatus according to claim 1, wherein the drive output restriction means releases at least a part of the restriction of the drive output when the magnitude of the steering angle falls below the predetermined angle, and the turning state indicator An apparatus that is executed when an understeer state quantity of values is decreasing.   3. The apparatus according to claim 1, wherein a limit amount of the drive output when the drive output limiting unit releases at least a part of the limit of the drive output is determined based on a vehicle speed of the vehicle. Features device.   4. The apparatus according to claim 1, wherein the drive output restriction means releases at least a part of the restriction of the drive output when the magnitude of the steering angle falls below the predetermined angle. The apparatus is executed when an understeer state quantity of the state index value decreases and the lateral acceleration of the vehicle is smaller than a predetermined acceleration.   5. The apparatus according to claim 1, wherein the drive output limiting means calculates a torque down rate of the vehicle drive apparatus based on the turning state index value and releases at least a part of the limit of the drive output. Is achieved by multiplying the torque down rate by a release gain.   6. The apparatus according to claim 1, wherein the turning state index value includes a function value of a target yaw rate and an actual yaw rate determined based on the steering angle, and the drive output limiting means has a magnitude of the steering angle. Is not greater than the predetermined angle, the understeer state quantity is increased, or the lateral acceleration of the vehicle is greater than the predetermined acceleration, the drive output is not limited. A device characterized by that.

Images