JP2015216724A - Braking-driving force control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately determine if a wheel is locked or slipped.SOLUTION: A motor ECU performs: calculating a vehicular real motion state quantity (real longitudinal force Fxreal, real roll moment Mxreal, real pitch moment Myreal, real yaw moment Mzreal) (S13); calculating four-wheel-real braking-driving force (F1real, F2real, F3real, F4real) on the basis of the real motion state quantity (S14); and calculating braking-driving force deviations (ΔF1, ΔF2, ΔF3, ΔF4) that are deviations between driver-requiring individual wheel braking-driving force (Freq1, Freq2, Freq3, Freq4) and real braking-driving force (F1real, F2real, F3real, F4real) (S15). The motor ECU determines that locking or slipping occurs at a wheel if a braking-driving force deviation larger than a determining threshold ΔFref is detected (S16-S17).

Description

  The present invention relates to a braking / driving force control device for a vehicle that generates driving force and braking force on wheels by an in-wheel motor.

  Conventionally, an in-wheel motor type vehicle in which a motor is incorporated in a wheel and the wheel is directly driven by this motor is known. In an in-wheel motor vehicle, braking / driving force (braking force and driving force) can be generated on the wheels by individually performing power running control or regenerative control of each motor.

  A part of the braking / driving force in the longitudinal direction of the wheel is converted into a vertical force of the vehicle body by the suspension. In particular, in an in-wheel motor type vehicle, the conversion efficiency into a vertical force is high, and a large vertical force can be generated in the vehicle body by controlling the braking / driving force. For example, an in-wheel motor braking / driving force control device proposed in Patent Document 1 detects vertical vibrations of a vehicle body and controls braking / driving forces of wheels so as to suppress the vertical vibrations.

JP 2006-109642 A

  By the way, in a situation where the wheels are locked or slipped, the vertical force of the vehicle body cannot be appropriately generated by controlling the braking / driving force. Therefore, antilock control (hereinafter referred to as ABS control) or traction control (hereinafter referred to as TRC control) is performed. In general, ABS control and TRC control calculate a wheel slip ratio from a wheel speed detected by a wheel speed sensor and a vehicle body speed calculated based on the wheel speed of four wheels, and the slip ratio exceeds a threshold value. It is carried out when it is determined that

  FIG. 4 shows μ-S characteristics representing the relationship between the friction coefficient μ of the road surface and the slip ratio S. This μ-S characteristic is one of the characteristics of a tire. When performing ABS control or TRC control, the tire performance can be maximized by controlling the braking / driving force based on the slip ratio S at which the friction coefficient μ is maximum. However, the maximum value of the friction coefficient μ (referred to as μ peak) is not always obtained with the same slip ratio, as can be seen from the characteristics of FIG. 4, and varies depending on the road surface condition, the type of tire, and the like. For this reason, the slip ratio S at which the friction coefficient μ is maximum cannot be estimated in advance. Therefore, even if the slip ratio is calculated based on the vehicle body speed and the wheel speed, the determination as to whether or not the slip ratio is excessive and the slip ratio should be reduced by the ABS control (lock state). In addition, it is impossible to accurately determine whether or not the slip ratio is excessive and the slip ratio should be reduced by TRC control (slip state).

  The present invention has been made to solve the above-described problems, and an object of the present invention is to appropriately determine the locked state and the slip state of a wheel.

In order to achieve the above object, the features of the present invention are:
In a braking / driving force control device for a four-wheel drive vehicle in which left and right front and rear wheels (10) can be driven and braked by a motor (30), and at least left and right front wheels or left and right rear wheels are driven and braked by a motor incorporated in the wheels. ,
A braking / driving torque control means for setting a target braking / driving force (Freq) of each wheel based on an operation amount of the driver and controlling a braking / driving torque of each motor so that each wheel generates the target braking / driving force. (50),
An actual motion state amount detecting means (S13) for detecting an actual motion state amount representing an actual motion state of the vehicle body when the braking / driving torque control means controls the braking / driving torque of each motor;
When the braking / driving torque control means controls the braking / driving torque of each motor, the degree to which the theoretical motion state quantity representing the motion state that should be theoretically taken of the vehicle body and the actual motion state quantity is deviated. Divergence index acquisition means (S14, S15) for acquiring motion state divergence indices (ΔF1 to ΔF4) to be expressed;
Wheel state determination means (S16, S17) for determining whether or not each wheel is in a locked state or a slip state based on the motion state deviation index acquired by the deviation index acquisition means.

  In the braking / driving force control device of the present invention, the left and right front and rear wheels can be driven and braked by a motor, and at least the left and right front wheels or the left and right rear wheels are driven and braked by a motor (in-wheel motor) incorporated in the wheels. Applies to four-wheel drive vehicles. For example, it is preferable to apply to a vehicle in which all four wheels (left and right front and rear wheels) are driven and braked by an in-wheel motor (referred to as braking / driving), but the left and right front wheels or the left and right rear wheels are controlled and driven by an in-wheel motor, The present invention may be applied to a vehicle driven and driven by a motor in which other wheels are fixed to the vehicle body side.

  The braking / driving torque control means sets the target braking / driving force of each wheel based on the operation amount of the driver, and controls the braking / driving torque of each motor so that each wheel generates the target braking / driving force. Thereby, braking / driving force is generated on the wheels. A part of the braking / driving force generated by the wheels (the force representing the driving force and the braking force) is converted into the vertical force of the vehicle body by the suspension. In particular, in the case of a vehicle in which wheels are controlled and driven by an in-wheel motor, the conversion efficiency into vertical force is high. Therefore, the motion state (posture) of the vehicle body can be controlled by the braking / driving force of the wheels.

  If the wheel is not locked or slipped, an appropriate braking / driving force can be generated on the wheel by the motor torque, but if the wheel is locked or slipped, the braking can be generated on the wheel. The driving force is reduced. Along with this, the vertical force acting on the vehicle body in proportion to the braking / driving force decreases, and the motion state of the vehicle body changes. In the present invention, the locked state and slip state of the wheel can be determined by capturing such a phenomenon.

  The actual motion state quantity detecting means detects an actual motion state quantity representing the actual motion state of the vehicle body when the braking / driving torque control means controls the braking / driving torque of each motor. For example, the actual motion state quantity detection means may detect the longitudinal force, roll moment, pitch moment, yaw moment, etc. of the vehicle body as the actual motion state quantity.

  The divergence index acquisition means is configured such that when the drive torque control means controls the braking / driving torque of each motor, the theoretical motion state quantity representing the motion state that can be taken theoretically and the actual motion state quantity are different. The motion state deviation index representing the degree of being is acquired. The actual motion state quantity and the theoretical motion state quantity do not deviate if the wheel is not locked or slipped, but deviate if the wheel is locked or slipped. Therefore, the wheel state determination means determines whether or not each wheel is in a locked state or a slip state based on the motion state deviation index acquired by the deviation index acquisition means.

  In the μ-S characteristic representing the relationship between the friction coefficient μ of the road surface and the slip ratio S, the braking / driving force of the wheel decreases when the slip ratio S exceeds the μ peak that is the maximum value of the friction coefficient μ. Also, the vertical force of the vehicle body is reduced. For this reason, the theoretical motion state quantity of the vehicle body that should be theoretically estimated based on the control command to each motor deviates from the actual motion state quantity. Therefore, by using the motion state divergence index indicating the degree of divergence between the theoretical motion state amount and the actual motion state amount, it is possible to appropriately determine the wheel lock state and the slip state. Thereby, for example, ABS control or TRC control can be appropriately performed. For example, the divergence index obtaining unit estimates the actual braking / driving force that is the actual braking / driving force generated at each wheel based on the actual motion state amount detected by the actual motion state detecting unit. A driving force estimating means may be provided, and a deviation between the target braking / driving force and the actual braking / driving force may be acquired as a motion state deviation index.

  Further, in the conventional device, in determining the locked state and the slip state of the wheel, the slip is determined based on the wheel speed detected by the wheel speed sensor provided on each wheel and the vehicle speed calculated from the wheel speeds of the four wheels. Calculate the rate. For this reason, when the wheel speed sensor fails or when all four wheels are locked or slipped simultaneously and the vehicle body speed cannot be properly calculated, it is difficult to determine the wheel lock state and the slip state. On the other hand, in the present invention, it is possible to appropriately determine without calculating the slip ratio.

One aspect of the present invention is:
The braking / driving torque control means includes:
The purpose of the present invention is to correct the magnitude of the braking / driving torque of the wheel braking / driving motor determined to be in the locked state or the slip state by the wheel state determining means so as to decrease as the motion state deviation index increases. .

  In one aspect of the present invention, the braking / driving torque control means determines the magnitude (absolute value) of the braking / driving torque of the wheel braking / driving motor determined by the wheel state estimating means as being locked or slipping. The larger the movement state deviation index, that is, the larger the difference between the theoretical movement state quantity and the actual movement state quantity, the smaller the correction. Therefore, the locked state and slip state of the wheel can be properly eliminated. Further, the tire performance can be satisfactorily extracted.

  In the above description, in order to help the understanding of the invention, the reference numerals used in the embodiments are attached to the configuration of the invention corresponding to the embodiments in parentheses, but each constituent element of the invention is represented by the reference numerals. It is not limited to the embodiments specified.

It is a schematic block diagram of the four-wheel drive vehicle by which the braking / driving force control apparatus which concerns on this embodiment is mounted. It is a figure showing the relationship between braking / driving force and vertical force. It is a flowchart showing a wheel state determination routine. It is a graph showing the μ-S characteristic for each road surface state. It is a graph showing the μ-S characteristic during driving. It is explanatory drawing showing the modification of arrangement | positioning of an in-wheel motor.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 schematically shows the configuration of a vehicle 1 on which the braking / driving force control device of this embodiment is mounted.

  The vehicle 1 includes a left front wheel 10fl, a right front wheel 10fr, a left rear wheel 10rl, and a right rear wheel 10rr. Motors 30fl, 30fr, 30rl, and 30rr are incorporated in the left front wheel 10fl, the right front wheel 10fr, the left rear wheel 10rl, and the right rear wheel 10rr, respectively.

  The motors 30fl, 30fr, 30rl, and 30rr are so-called in-wheel motors, which are arranged under the spring of the vehicle 1 together with the left front wheel 10fl, the right front wheel 10fr, the left rear wheel 10rl, and the right rear wheel 10rr, respectively, and the motor torque is set to the left. The front wheel 10fl, the right front wheel 10fr, the left rear wheel 10rl, and the right rear wheel 10rr are communicably connected. In the vehicle 1, by independently controlling the rotation of each motor 30fl, 30fr, 30rl, 30rr, the driving force generated on the left front wheel 10fl, the right front wheel 10fr, the left rear wheel 10rl, and the right rear wheel 10rr and The braking force can be controlled independently.

  The left front wheel 10fl, the right front wheel 10fr, the left rear wheel 10rl, and the right rear wheel 10rr are suspended on the vehicle body B by independent suspensions 20fl, 20fr, 20rl, and 20rr through casings of motors 30fl, 30fr, 30rl, and 30rr, respectively. ing. Suspensions 20fl, 20fr, 20rl, and 20rr are connecting mechanisms that connect the vehicle body B and the wheels 10fl, 10fr, 10rl, and 10rr, a suspension link mechanism, and a suspension spring that supports a load in the vertical direction and absorbs an impact. And a shock absorber for attenuating vibration on the spring (vehicle body B). As the suspensions 20fl, 20fr, 20rl, and 20rr, a known four-wheel independent suspension type suspension such as a wishbone type suspension or a strut type suspension can be adopted.

  Hereinafter, when it is not necessary to specify any of the wheels 10fl, 10fr, 10rl, 10rr, the suspensions 20fl, 20fr, 20rl, 20rr, the motors 30fl, 30fr, 30rl, 30rr, the wheels 10, The suspension 20 and the motor 30 are called. In addition, when specifying a component provided on the front wheels 10fl and 10fr side, “f” is added to the end of the symbol, and when specifying a component provided on the rear wheels 10rl and 10rr, “r” is added to the end of the symbol. .

  Each motor 30 is, for example, a brushless motor. Each motor 30 is connected to a motor driver 35. The motor driver 35 is, for example, an inverter, and four sets are provided so as to correspond to the motors 30. The motor driver 35 converts the DC power supplied from the battery 60 into AC power, and the AC power is independent of each motor 30. And supply. Thereby, each motor 30 is drive-controlled to generate torque and apply driving force to each wheel 10. Thus, supplying electric power to the motor 30 to generate driving torque is referred to as power running.

  Each motor 30 also functions as a generator, and can generate electric power by the rotational energy of each wheel 10 and regenerate the generated power to the battery 60 via the motor driver 35. The regenerative braking torque generated by the power generation of the motor 30 gives a braking force to the wheel 10. Although each wheel 10 is provided with a friction brake device, since it is not directly related to the present invention, illustration and description are omitted.

  The motor driver 35 is connected to the motor control electronic control unit 50. The motor control electronic control unit 50 (hereinafter referred to as a motor ECU 50) includes a microcomputer including a CPU, a ROM, a RAM, and the like as a main part, and executes various programs to independently control the operation of each motor 30. To do. The motor ECU 50 connects an operation state detection device 40 that detects an operation state operated by the driver to drive the vehicle, and a movement state detection device 45 that detects the movement state of the vehicle, and detects these detection devices 40 and 45. The detection signal output from is input.

  The operation state detection device 40 is an accelerator sensor that detects the driver's accelerator operation amount from the accelerator pedal depression amount (or angle, pressure, etc.), and the driver's brake operation from the brake pedal depression amount (or angle, pressure, etc.). A brake sensor that detects the amount, a steering angle sensor that detects the amount of steering operation by the driver operating the steering wheel, and the like. The motion state detection device 45 is a wheel speed sensor that detects a wheel speed that is the rotational speed of each wheel 10, and a vehicle speed sensor that calculates and detects a vehicle speed that is the traveling speed of the vehicle body B based on the wheel speeds of the four wheels. A yaw rate sensor that detects the yaw rate of the vehicle body B, a sprung acceleration sensor that detects vertical acceleration of the vehicle body B (on the spring) at each wheel position, a longitudinal acceleration sensor that detects longitudinal acceleration in the longitudinal direction of the vehicle body B, and the vehicle body B A lateral acceleration sensor that detects lateral acceleration in the left-right direction, a pitch rate sensor that detects the pitch rate of the vehicle body B, a roll rate sensor that detects the roll rate of the vehicle body B, a stroke sensor that detects the stroke amount of each suspension 20, A combination of an unsprung acceleration sensor for detecting vertical acceleration in the vertical direction below the unsprung wheel 10 and the like. It is made. In addition, about the sensor value containing a direction element, a direction is identified by the code | symbol. When discussing the magnitude of the sensor value, the absolute value is used.

  When the motor control routine is executed, the motor ECU 50 sets the driver requested wheel braking drive force Freq for each wheel 10 based on the accelerator operation amount and the brake operation amount detected by the operation state detection device 40. For example, the motor ECU 50 sets a driver-requested total driving force that increases as the accelerator operation amount increases or a driver-requested total braking force that increases as the brake operation amount increases, based on a preset braking / driving force map. The driver-requested total driving force or the driver-requested total braking force is distributed to the four wheels at a predetermined distribution ratio, thereby setting the driver-requested wheel braking / driving force Freq for each wheel 10. The driver-requested wheel braking / driving force Freq corresponds to the target braking / driving force in the present invention.

  The motor ECU 50 calculates a target torque Treq (target drive torque Treq or target regenerative braking torque Treq) corresponding to each wheel braking driving force Freq requested by the driver so that each motor 30 generates the target torque Treq (target torque Treq). The motor driver 35 is controlled so that the target current corresponding to the? As a result, a braking / driving force corresponding to the driver-requested wheel braking / driving force Freq is generated at each wheel 10. The driver-required wheel braking drive force Freq is a general term for the driver-required wheel braking / driving forces in the four wheels. As described above, Freq1 is used for the left front wheel, Freq2 is used for the right front wheel, Freq3 is used for the left rear wheel, and Freq4 is used for the right rear wheel.

  As shown in FIG. 2, the suspension 20 that suspends each wheel 10 has an instantaneous rotation center Cf (an instantaneous center of the front wheel 10f with respect to the vehicle body B) in the front wheel suspension 20f at the rear and above the front wheel 10f in a side view of the vehicle. The instantaneous rotation center Cr in the rear wheel suspension 20r (the instantaneous center of the rear wheel 10r with respect to the vehicle body B) is positioned forward and above the rear wheel 10r. In addition, the angle (smaller angle) formed between the line connecting the ground point of the front wheel 10f and the instantaneous rotation center Cf and the ground horizontal plane is θf, and the line connecting the ground point of the rear wheel 10r and the instantaneous rotation center Cr and the ground horizontal plane. Let θr be the angle formed by (the smaller angle). In the vehicle according to the present embodiment, θr is larger than θf (θf <θr), but may have the opposite relationship. Hereinafter, θf is referred to as an instantaneous rotation angle θf, and θr is referred to as an instantaneous rotation angle θr.

  In such a configuration (geometry) of the suspension 20, when a driving torque is applied to the front wheel 10f, a forward force FxfD with respect to the traveling direction of the vehicle is applied to the ground point of the front wheel 10f as shown in FIG. The vertical force FzfD acting and urging the vehicle body B downward by this force FxfD is generated at the ground contact point of the front wheel 10f. Therefore, driving the front wheel 10f causes a force in the direction of sinking the vehicle body B. On the contrary, as shown in FIG. 2B, when braking torque is applied to the front wheel 10f, a backward force FxfB acts on the ground contact point of the front wheel 10f with respect to the traveling direction of the vehicle, and the vehicle body B is caused by this force FxfB. A vertical force FzfB that urges upward is generated at the ground contact point of the front wheel 10f. Therefore, a force in a direction to lift the vehicle body B acts by braking the front wheel 10f. Further, as shown in FIG. 2A, when a driving torque is applied to the rear wheel 10r, a forward force FxrD is applied to the grounding point of the rear wheel 10r with respect to the traveling direction of the vehicle, and the vehicle body B is caused by this force FxrD. A vertical force FzrD is applied to the grounding point of the rear wheel 10r. Therefore, driving the rear wheel 10r causes a force in a direction to lift the vehicle body B. Conversely, as shown in FIG. 2B, when braking torque is applied to the rear wheel 10r, a backward force FxrB acts on the grounding point of the rear wheel 10r with respect to the traveling direction of the vehicle. A vertical force FzrB that urges B downward is generated at the ground contact point of the rear wheel 10r. Therefore, a force in the direction of sinking the vehicle body B acts by braking the rear wheel 10r. In this way, the suspension 20 converts the driving force and braking force of the wheel 10 into the vertical force of the vehicle body B.

  The magnitude of the vertical force acting on the vehicle body B is a value obtained by multiplying the braking / driving force Fxf (FxfD or FxfB) by tan (θf) on the front wheel 10f side, and the braking / driving force Fxr (FxrD or FxrB on the rear wheel 10r side). ) Multiplied by tan (θr). The function of converting the braking / driving force into the vertical force of the vehicle body B is mainly due to the link mechanism of the suspension 20, but the final vertical force conversion rate is finally determined by the positions of the instantaneous rotation centers Cf and Cr. Since the instantaneous rotation centers Cf and Cr are also related to the suspension spring and the shock absorber, the entire suspension 20 can be regarded as converting the braking / driving force into the vertical force of the vehicle body B.

  Therefore, by controlling the driving force or braking force (braking / driving force) of the wheel 10, a vertical force can be applied to the vehicle body B, and the motion state control (posture control) of the vehicle body B can be performed. it can. Further, since the braking / driving force of the wheel 10 is reduced when the wheel 10 is locked and slipped, the vertical force acting on the vehicle body B is also reduced. For example, as indicated by broken line arrows in FIG. 2A, when the driving forces FxfD and FxrD are reduced to FxfD 'and FxrD', the vertical forces FzfD and FzrD are also reduced to FzfD 'and FzrD'. Further, as indicated by broken line arrows in FIG. 2B, when the braking forces FxfB and FxrB are reduced to FxfB 'and FxrB', the vertical forces FzfB and FzrB are also reduced to FzfB 'and FzrB'. For this reason, the movement state of the vehicle body B changes when the wheel 10 is locked and slipped. Therefore, based on the change in the motion state of the vehicle body B, the locked state and slip state of the wheel 10 can be determined (the presence or absence of lock and slip is determined).

ここで、Ｆx1は左前輪１０flの制駆動力、Ｆx2は右前輪１０frの制駆動力、Ｆx3は左後輪１０rlの制駆動力、Ｆx4は右後輪１０rrの制駆動力を表す。また、左辺第２項のａ11〜ａ14、ａ21〜ａ24、ａ31〜ａ34、ａ41〜ａ44は、車両モデルを表す定数である。また、右辺のＦxは、車両Ｂの前後方向の力、Ｍxは、車両の重心を通る前後方向軸（ロール軸）回りの車体Ｂのロール運動量を表すロールモーメント、Ｍyは、車両の重心を通る左右方向軸（ピッチ軸）回りの車体Ｂのピッチ運動量を表すピッチモーメント、Ｍzは、車両の重心を通る鉛直方向軸（ヨー軸）回りの車体Ｂのヨー運動量を表すヨーモーメントを表す。 Here, the principle of determining the locked state and the slip state of the wheel 10 based on the change in the motion state of the vehicle body B will be described. The braking / driving force of the four wheels and the motion state quantity of the vehicle body B have a relationship represented by the following expression (1).

Here, Fx1 represents the braking / driving force of the left front wheel 10fl, Fx2 represents the braking / driving force of the right front wheel 10fr, Fx3 represents the braking / driving force of the left rear wheel 10rl, and Fx4 represents the braking / driving force of the right rear wheel 10rr. Further, a11 to a14, a21 to a24, a31 to a34, and a41 to a44 in the second term on the left side are constants representing the vehicle model. Further, Fx on the right side is a force in the front-rear direction of the vehicle B, Mx is a roll moment representing the roll momentum of the vehicle body B around the front-rear direction axis (roll axis) passing through the center of gravity of the vehicle, and My passes through the center of gravity of the vehicle. Pitch moment representing the pitch momentum of the vehicle body B about the left-right axis (pitch axis), Mz, represents the yaw moment representing the yaw momentum of the vehicle body B about the vertical axis (yaw axis) passing through the center of gravity of the vehicle.

  Therefore, when the motor 30 of each wheel is controlled in accordance with the driver requested wheel braking driving force Freq (Freq1, Freq2, Freq3, Freq4), the left side (Fx1, Fx2, Fx3, Fx4) of the above equation (1) is satisfied. By substituting each wheel braking drive force (Freq1, Freq2, Freq3, Freq4) requested by the driver, a theoretical motion state quantity (Fx, Mx, My, Mz) representing a motion state that the vehicle body B should be able to take theoretically is calculated. be able to. When the wheel 10 is locked or slipped, the braking / driving force that can be generated by the wheel 10 is reduced, so that the vertical force acting on the vehicle body B is also reduced. For this reason, the motion state of the vehicle body B changes according to the locked state or slip state of the four wheels. Therefore, the actual motion state quantity deviates from the theoretical motion state quantity obtained by using the driver requested wheel drive force Freq.

  The actual motion state amount (referred to as actual motion state amount) can be estimated from the sensor value detected by the motion state detection device 45. For example, the actual longitudinal force Fxreal of the vehicle body B can be estimated based on the sensor value detected by the longitudinal acceleration sensor. Further, the actual roll moment Mxreal and the actual pitch moment Myreal of the vehicle body B can be estimated based on sensor values detected by a sprung vertical acceleration sensor, a stroke sensor, or the like provided for each wheel. Further, the actual yaw moment Mzreal of the vehicle body can be estimated based on the sensor value detected by the yaw rate sensor.

  As shown in FIG. 5, the driving force of the wheel 10 decreases when the slip ratio S becomes larger than the μ peak. As with the driving force, the braking force also decreases when the slip ratio S becomes larger than the μ peak. Therefore, by comparing the theoretical motion state quantities (Fx, Mx, My, Mz) and the actual motion state quantities (Fxreal, Mxreal, Myreal, Mzreal), the slip ratio S of the wheel 10 exceeds the μ peak. It can be determined whether or not. As a result, even if the μ peak changes depending on the road surface condition or the type of tire, it is possible to determine whether the wheel 10 is locked or slipped corresponding to the actual μ peak. For example, if the actual motion state quantity (Fxreal, Mxreal, Myreal, Mzreal) is not deviated from the theoretical motion state quantity (Fx, Mx, My, Mz), whether the wheel 10 is locked or slipping. It can be determined that there is no. On the other hand, if the actual motion state quantity (Fxreal, Mxreal, Myreal, Mzreal) is deviated from the theoretical motion state quantity (Fx, Mx, My, Mz), the wheel 10 is locked or slipped. It can be determined that there is.

  The slip ratio S is represented by ((body speed−wheel speed) / body speed) × 100 (%) during vehicle braking, and ((drive wheel speed−body speed) / drive wheel during vehicle acceleration. Speed) × 100 (%).

この実運動状態量から推定される各車輪１０の制駆動力（Ｆ1real，Ｆ2real，Ｆ3real，Ｆ4real）を実制駆動力と呼ぶ。尚、Ｆ1realは左前輪１０flの実制駆動力、Ｆ2realは右前輪１０frの実制駆動力、Ｆ3realは左後輪１０rlの実制駆動力、Ｆ4realは右後輪１０rrの実制駆動力を表す。 If the above equation (1) is used, as shown in the following equation (2), the braking / driving force (F1real, F2real, F3real) generated in each wheel 10 from the actual motion state quantity (Fxreal, Mxreal, Myreal, Mzreal). , F4real) can be estimated.

The braking / driving force (F1real, F2real, F3real, F4real) of each wheel 10 estimated from this actual motion state quantity is called actual braking / driving force. F1real represents the actual driving force of the left front wheel 10fl, F2real represents the actual driving force of the right front wheel 10fr, F3real represents the actual driving force of the left rear wheel 10rl, and F4real represents the actual driving force of the right rear wheel 10rr.

  The actual braking / driving force is a value reflecting the actual motion state quantity. Therefore, in the present embodiment, for each wheel 10, the driver-requested wheel braking / driving forces (Freq1, Freq2, Freq3, Freq4) and the actual braking / driving forces (F1real, F2real, F3real, F4real) are compared. Based on the difference, the actual movement state quantity (Fxreal, Mxreal, Myreal, Mzreal) is the cause of the deviation from the theoretical movement state quantity (Fx, Mx, My, Mz), that is, the locked state or The wheel 10 in the slip state is specified.

  For example, the braking / driving force deviation ΔF1 (= Freq1-F1real) of the left front wheel 10fl, the braking / driving force deviation ΔF2 (= Freq2-F2real) of the right front wheel 10fr, and the braking / driving force deviation ΔF3 (= Freq3-F3real) of the left rear wheel 10rl. If the braking / driving force deviation ΔF4 (= Freq4−F4real) of the right rear wheel 10rr is calculated and it is determined whether or not the determination threshold ΔFref is exceeded for each braking / driving force deviation ΔF1, ΔF2, ΔF3, ΔF4. Good. Thereby, it is possible to determine that the wheel 10 whose braking / driving force deviations ΔF1, ΔF2, ΔF3, and ΔF4 exceed the determination threshold value ΔFref is a wheel in a locked state or a slip state.

  The braking / driving force deviations ΔF1, ΔF2, ΔF3, and ΔF4 are such that the actual motion state quantities (Fxreal, Mxreal, Myreal, Mzreal) are deviated from the theoretical motion state quantities (Fx, Mx, My, Mz). The larger the value, the larger. Therefore, the braking / driving force deviations ΔF1, ΔF2, ΔF3, and ΔF4 can be used as the motion state deviation index of the present invention. Hereinafter, the braking / driving force deviations ΔF1, ΔF2, ΔF3, and ΔF4 are simply referred to as braking / driving force deviations ΔF when it is not necessary to distinguish the corresponding wheels 10.

  Next, the control process at the time of slipping and locking of the wheel 10 performed by the motor ECU 50 will be described. FIG. 3 shows a wheel state determination routine executed by the motor ECU 50. The wheel state determination routine is repeatedly executed at a predetermined short calculation cycle.

  When the wheel state determination routine is activated, the motor ECU 50 determines in step S11 whether or not the determination permission condition for the locked state and the slip state of the wheel 10 is satisfied. In the present embodiment, two AND conditions are set as determination permission conditions: the vehicle is not traveling on a rough road (first condition), and the steering wheel is maintained at a neutral position (second condition). ing.

  With respect to the first condition, the motor ECU 50 calculates, for example, a wheel acceleration representing a change amount per unit time of the wheel speed of each wheel detected by the wheel speed sensor of the motion state detection device 45, and calculates the wheel acceleration of the four wheels. When the average value of absolute values (or the maximum value, minimum value, etc. may be used) exceeds the rough road determination reference value, it is determined that the vehicle is traveling on a rough road. The bad road determination is not limited to using the wheel acceleration. For example, it is determined whether or not the absolute value of the unsprung vertical acceleration detected by the unsprung acceleration sensor exceeds the rough road determination reference value. A well-known method can be adopted.

  Further, regarding the second condition, the motor ECU 50 determines whether or not the steering handle is maintained at the neutral position for a predetermined time or more based on the steering operation amount detected by the steering angle sensor of the operation state detection device 40. This predetermined time is set to a time required until the steering operation is completed and the vehicle state is stabilized.

  When the determination permission condition is not satisfied (S11: No), the motor ECU 50 once ends this routine. Then, this routine is repeated at a predetermined calculation cycle.

  On the other hand, if the determination permission condition is satisfied (S11: Yes), the motor ECU 50 reads the driver-requested wheel braking drive forces Freq (Freq1, Freq2, Freq3, Freq4) in step S12. In parallel with the lock / slip control routine, the motor ECU 50 executes a motor control routine for controlling the braking / driving torque of the motor 10 according to the driver requested wheel braking / driving force Freq. In step S12, the motor control routine is executed. Each wheel braking driving force Freq calculated by the execution of is read.

  Subsequently, in step S13, the motor ECU 50 estimates the actual motion state amount of the vehicle body B by calculation based on the sensor value detected by the motion state detection device 45. In the present embodiment, as described above, the actual longitudinal force Fxreal, the actual roll moment Mxreal, the actual pitch moment Myreal, and the actual yaw moment Mzreal of the vehicle body B are estimated as the actual motion state quantities.

  Subsequently, in step S14, the motor ECU 50 calculates the actual braking / driving force (F1real, F2real, F3real, F4real) of each wheel 10 estimated from the actual motion state quantity using the above equation (2).

  Subsequently, in step S15, the motor ECU 50 determines the difference between the driver-requested wheel braking / driving force (Freq1, Freq2, Freq3, Freq4) and the actual braking / driving force (F1real, F2real, F3real, F4real) for each wheel 10. A certain braking / driving force deviation ΔF1 (= Freq1-F1real), ΔF2 (= Freq2-F2real), ΔF3 (= Freq3-F3real), and ΔF4 (= Freq4-F4real) are calculated.

  Subsequently, in step S16, the motor ECU 50 compares the deviations ΔF1, ΔF2, ΔF3, and ΔF4 in each wheel 10 with a predetermined determination threshold value ΔFref, and all of the braking / driving force deviations ΔF1, ΔF2, ΔF3, and ΔF4 are compared. Is less than or equal to the determination threshold ΔFref. When all of the braking / driving force deviations ΔF1, ΔF2, ΔF3, and ΔF4 are equal to or smaller than the determination threshold value ΔFref (S16: Yes), the motor ECU 50 determines that there is no wheel 10 in the locked state or the slipped state. To end this routine.

  On the other hand, if any one of the braking / driving force deviations ΔF1, ΔF2, ΔF3, and ΔF4 exceeds the determination threshold ΔFref (S16: No), the motor ECU 50 determines that the braking / driving greater than the determination threshold ΔFref in step S17. It is determined that the wheel 10 in which the force deviation ΔF occurs is a wheel in a locked state or a slip state (hereinafter referred to as a target wheel). That is, the target wheel is specified from the four wheels.

  Subsequently, in step S18, the motor ECU 50 determines whether or not the driver-requested wheel braking driving force Freq is a driving force. When the driver-requested wheel braking drive force Freq is a drive force (S18: Yes), TRC control is performed in step S19 because the target wheel is in a slip state. On the other hand, when the driver-requested wheel braking drive force Freq is a braking force (S18: No), the ABS is controlled in step S20 because the target wheel is locked.

  In the TRC control performed in step S19, the target drive torque Treq of the target wheel may be reduced by a conventionally known method, but in this embodiment, the braking / driving force deviation ΔF of the target wheel is increased. A value (Ktrc × ΔF) obtained by multiplying the adjustment gain Ktrc is converted into a motor torque, and the target drive torque Treq is corrected using the adjustment torque ΔT that is the converted motor torque. That is, the motor ECU 50 sets a value (Treq−ΔT) obtained by subtracting the adjustment torque ΔT proportional to the braking / driving force deviation ΔF from the target drive torque Treq as a new target drive torque Treq. Further, the total driving force of the four wheels does not change by distributing and adding the amount (adjustment torque ΔT) of the target driving torque Treq of the target wheel to the target driving torque Treq of other wheels (non-target wheels). Like that. In this case, for example, the adjustment torque ΔT may be distributed according to the ground load distribution ratio of the non-target wheels to compensate for the decrease in the driving force of the target wheels. The motor ECU 50 controls the drive of the motor 30 according to the target drive torque Treq corrected in this way in a motor control routine executed in parallel with this routine. The adjustment gain Ktrc is a value set in advance, but may be a value set independently for each wheel 10.

  Also, with respect to the ABS control performed in step S20, the target regenerative braking torque Treq of the target wheel may be reduced by a conventionally known method, but in this embodiment, the braking / driving of the target wheel is performed. A value (Kabs × ΔF) obtained by multiplying the force deviation ΔF by the adjustment gain Kabs is converted into motor torque, and the target regenerative braking torque Treq is corrected using the adjustment torque ΔT that is the converted motor torque. That is, the motor ECU 50 sets a value (Treq−ΔT) obtained by subtracting the adjustment torque ΔT proportional to the braking / driving force deviation ΔF from the target regenerative braking torque Treq as a new target regenerative braking torque Treq. Further, the total braking force of the four wheels can be obtained by distributing and adding the reduced amount (adjustment torque ΔT) of the target regenerative braking torque Treq of the target wheel to the target regenerative braking torque Treq of other wheels (non-target wheels). Do not change. In this case, for example, the adjustment torque ΔT may be distributed according to the ground load distribution ratio of the non-target wheels so as to compensate for the decrease in the braking force of the target wheels. The motor ECU 50 drives and controls the motor 30 according to the target regenerative braking torque Treq corrected in this way in a motor drive control routine executed in parallel with this routine. The adjustment gain Kabs is a value set in advance, but may be a value set independently for each wheel 10.

  When the motor ECU 50 performs the TRC control in step S19 or the ABS control in step S20, the routine is temporarily terminated. Then, this routine is repeated at a predetermined calculation cycle.

  According to the braking / driving force control device of the present embodiment described above, the lock state and slip of each wheel 10 are determined using the motion state divergence index indicating the degree to which the actual motion state amount and the theoretical motion state amount deviate. Therefore, it is possible to make an appropriate determination according to the road surface condition. Therefore, even if the μ peak changes due to road surface conditions or the like, ABS control or TRC control can be started at an appropriate timing beyond the μ peak. As a result, the ABS control or the TRC control is not started earlier than necessary, and the wheel 10 can be controlled in the vicinity of the μ peak, and the tire performance can be satisfactorily extracted.

  Also, as the motion state deviation index, the deviation between the driver requested wheel drive force (Freq1, Freq2, Freq3, Freq4) and the actual drive force (F1real, F2real, F3real, F4real) estimated from the actual motion state quantity. Since the braking / driving force deviation (ΔF1, ΔF2, ΔF3, ΔF4) is used, it is possible to easily identify the target wheel and determine the locked state and the slip state of each wheel 10.

  Further, since it is not necessary to use the slip ratio as in the conventional device in determining the locked state and the slip state of each wheel 10, if the wheel speed sensor breaks down or all four wheels are locked or slipped simultaneously, the vehicle body Even when the speed cannot be properly calculated, the determination of the locked state and the slip state of the wheel 10 can be properly performed.

  Although the braking / driving force control device according to the present embodiment has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, in the present embodiment, as shown in FIG. 6A, application to a vehicle 1 in which all of the left and right front and rear wheels 10 are independently driven by an in-wheel motor 30 is described. 6B, the left and right rear wheels 10r are independently driven by an in-wheel motor 30r, and the left and right front wheels 10f are applied to a vehicle 2 that is commonly driven by a hybrid system 7. Also good. 6C, the left and right front wheels 10f are independently driven by the in-wheel motor 30, and the left and right rear wheels 10r are commonly driven by the hybrid system 7. May be. The hybrid system 7 includes a motor and an internal combustion engine on the side of the vehicle body B, and is a system capable of braking and driving the wheels 10 with a single motor. The determination of the locked state and the slip state of the wheel 10 may be performed when the hybrid system 7 controls and drives the wheel 10 by a single motor. The reason is that the torque applied to the wheel 10 by the motor can be accurately controlled as compared with the internal combustion engine, and as a result, the estimation of the motion state quantity is accurate.

  In the present embodiment, the second condition (the steering wheel is maintained at the neutral position) is set as one of the determination permission conditions for the locked state and the slip state of the wheel 10, but this is calculated. The second condition can be omitted as long as the configuration can calculate a theoretical motion state quantity (which may be a physical quantity corresponding to the theoretical motion state quantity) according to the steering operation amount. .

  1, 2, 3 ... Vehicle, 10fl, 10fr, 10rl, 10rr ... Wheel, 20fl, 20fr, 20rl, 20rr ... Suspension, 30fl, 30fr, 30rl, 30rr ... Motor, 40 ... Operation state detection device, 45 ... Motion state detection 50, an electronic control unit (motor ECU) for motor control, B, a vehicle body, Cf, Cr, a center of instantaneous rotation, Freq1, Freq2, Freq3, Freq4, driver request each wheel braking drive force, F1real, F2real, F3real, F4real ... actual braking / driving force, ΔF1, ΔF2, ΔF3, ΔF4 ... braking / driving force deviation.

Claims (2)

In a braking / driving force control device for a four-wheel drive vehicle in which left and right front and rear wheels can be driven and braked by a motor, and at least left and right front wheels or left and right rear wheels are driven and braked by a motor incorporated in the wheels,
Braking / driving torque control means for setting the target braking / driving force of each wheel based on the operation amount of the driver, and controlling the braking / driving torque of each motor so that each wheel generates the target braking / driving force;
An actual motion state detection means for detecting an actual motion state amount representing an actual motion state of the vehicle body when the braking / driving torque control means is controlling the braking / driving torque of each motor;
When the braking / driving torque control means controls the braking / driving torque of each motor, the degree to which the theoretical motion state quantity representing the motion state that should be theoretically taken of the vehicle body and the actual motion state quantity is deviated. A divergence index acquisition means for acquiring a motion state divergence index to represent;
A braking / driving force control device comprising: wheel state determination means for determining whether or not each wheel is in a locked state or a slip state based on the motion state deviation index acquired by the deviation index acquisition means. The braking / driving force control device according to claim 1,
The braking / driving torque control means includes:
The braking / driving force for correcting the braking / driving torque of the motor for braking / driving the wheel determined to be in the locked state or the slip state by the wheel state determining means so as to decrease as the motion state deviation index increases. Control device.

Images