JP6577850B2 - Vehicle control apparatus and vehicle control method - Google Patents

Description

  The present invention relates to a vehicle control device and a vehicle control method.

  Conventionally, for example, in Patent Document 1 below, a direct yaw moment (target yaw moment) DYM for suppressing an undesirable yaw behavior caused by, for example, vehicle slip or the like is calculated, and the direct yaw moment DYM is calculated. Describes a technique for increasing / decreasing the output of each in-wheel motor so that is output.

JP 2009-143310 A

  However, the technique described in Patent Document 1 has a problem that an undesirable yaw behavior once occurs because the output of each in-wheel motor is increased or decreased when an undesirable yaw behavior occurs in the vehicle. For this reason, it is difficult to stabilize the behavior of the vehicle with high accuracy.

  Further, in the technique described in Patent Document 1, since it can be determined for the first time that an undesirable yaw behavior has occurred, the vehicle is in a limit state, and one slip must be permitted. A slip will cause anxiety to the driver.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to correct a vehicle body additional moment for turning assist before a slip occurs in the vehicle. A new and improved vehicle control apparatus and vehicle control method are provided.

In order to solve the above-described problem, according to one aspect of the present invention, a vehicle body additional moment calculation unit that calculates a vehicle body additional moment to be applied to the vehicle body independently of the steering system based on the yaw rate of the vehicle, and a vehicle slip Based on the angle and the tire rudder angle, a turning restoration yaw moment calculating unit for calculating a turning restoring yaw moment for restoring the turning state of the vehicle to a straight traveling state, and a vehicle slip angular velocity that is a temporal change rate of the vehicle slip angle are calculated. A vehicle body slip angular velocity calculating unit to calculate, a turn assist control gain calculating unit for calculating a turn assist control gain for correcting the vehicle body additional moment based on the turn restoring yaw moment and the vehicle slip angular velocity, and the turn assist based on the control gain, and a correcting unit for correcting the vehicle body additional moment, the revolving Assist When the turning recovery yaw moment exceeds a predetermined threshold and increases in a direction opposite to the direction in which the turning state of the vehicle is restored to the straight traveling state, the control gain calculation unit increases the turning recovery yaw moment. There is provided a vehicle control device that lowers the turning assist control gain and lowers the predetermined threshold as the vehicle body slip angular velocity increases .

  Further, the turning restoration yaw moment calculation unit may calculate the turning restoration yaw moment based on a map that defines a relationship between the vehicle body slip angle, the tire rudder angle, and the turning restoration yaw moment. good.

  The turning restoration yaw moment calculation unit may calculate the turning restoration yaw moment based on the longitudinal acceleration of the vehicle in addition to the vehicle slip angle and the tire steering angle.

  The turning restoration yaw moment may be determined from a self-aligning torque determined from a vehicle specification value and a lateral force of the tire.

  A target yaw rate calculating unit that calculates a target yaw rate based on a steering angle and a vehicle speed; a vehicle yaw rate calculating unit that calculates a yaw rate model value from a vehicle model; a yaw rate sensor that detects an actual yaw rate of the vehicle; and the yaw rate A feedback yaw rate calculation unit that distributes the yaw rate model value and the actual yaw rate based on a difference between the model value and the actual yaw rate, and calculates a feedback yaw rate from the yaw rate model value and the actual yaw rate; The additional moment calculation unit may calculate the vehicle body additional moment based on a difference between the target yaw rate and the feedback yaw rate.

  Further, a motor request torque calculation unit that calculates a motor request torque for individually controlling a motor that drives each of the rear left and right wheels of the vehicle based on the vehicle body additional moment may be provided.

In order to solve the above problem, according to another aspect of the present invention, a step of calculating a vehicle body additional moment to be applied to the vehicle body independently of the steering system based on a yaw rate of the vehicle, and a vehicle slip angle And a step of calculating a turning restoration yaw moment for restoring the turning state of the vehicle to a straight traveling state based on the tire rudder angle, a step of calculating a vehicle slip angular velocity that is a temporal change rate of the vehicle slip angle, based on the swivel restoration yaw moment and the vehicle slip angular velocity, and calculating the turning assist control gain for correcting the vehicle body additional moment on the basis of the turning assist control gain, and correcting the vehicle body additional moment the provided, in the step of calculating the turning assist control gain, the swivel restoration yaw moment When the vehicle turns in a direction opposite to the direction in which the turning state of the vehicle is restored to the straight traveling state exceeding a predetermined threshold value, the turning assist control gain is decreased as the turning restoring yaw moment increases, and the vehicle slip A vehicle control method is provided in which the predetermined threshold value is lowered as the angular velocity increases .

  As described above, according to the present invention, it is possible to correct the vehicle body additional moment for turning assist before the vehicle slips.

It is a mimetic diagram showing a vehicle concerning one embodiment of the present invention. It is a schematic diagram for demonstrating general yaw rate feedback control. It is a figure which shows the relationship between the slip angle of a wheel, and a lateral acceleration. It is a characteristic view which shows the relationship between the slip ratio of a tire, and the longitudinal force. It is a schematic diagram for demonstrating self-aligning torque. It is a characteristic view which shows the relationship between a slip angle and a self-aligning torque. It is a characteristic view showing a map for calculating a turning restoration moment (turning yaw moment) according to the present embodiment. It is a figure which shows the relationship between the front-back force and lateral force of a rear wheel. It is a schematic diagram which shows in detail the structure of the control apparatus which concerns on this embodiment, and its periphery. It is a schematic diagram which shows the gain map at the time of the weighting gain calculation part calculating the weighting gain a. It is a flowchart which shows the whole process of this embodiment. It is a flowchart which shows the process of step S122 of FIG. It is a flowchart which shows the process in which the vehicle yaw rate calculation part 206 calculates the yaw rate model value (gamma) _clc. It is a flowchart which shows the process which calculates additional torque Tvmot. It is a flowchart which shows the process which calculates turning assistance gain (beta) G. FIG. 6 is a characteristic diagram showing a turning assist gain βG calculated in steps S252 and S254. FIG. 10 is a characteristic diagram showing a turning assist gain βG calculated in step S256. It is a characteristic view for demonstrating the effect at the time of performing control concerning this embodiment. It is a characteristic view for demonstrating the effect at the time of performing control concerning this embodiment. It is a characteristic view for demonstrating the effect at the time of performing control concerning this embodiment. It is a characteristic view for demonstrating the effect at the time of performing control concerning this embodiment.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  First, with reference to FIG. 1, the structure of the vehicle 1000 which concerns on one Embodiment of this invention is demonstrated. FIG. 1 is a schematic diagram showing a vehicle 1000 according to the present embodiment. As shown in FIG. 1, a vehicle 1000 includes driving force generators (motors) 108, 110, 112, driving front wheels 100 and 102, rear wheels 104 and 106, front wheels 100 and 102, and rear wheels 104 and 106. 114, the gear boxes 116, 118, 120, 122 and the motors 108, 110, 112, 114 that transmit the driving force of the motors 108, 110, 112, 114 to the front wheels 100, 102 and the rear wheels 104, 106, respectively. Inverters 123, 124, 125, 126 to be controlled, wheel speed sensors 127, 128 for detecting the respective wheel speeds (vehicle speed V) of the rear wheels 104, 106, a steering wheel 130 for steering the front wheels 100, 102, a longitudinal acceleration sensor 132, lateral acceleration sensor 134, battery 136, rudder angle sensor 138, parameter Steering mechanism 140, a yaw rate sensor 142, an inhibitor position sensor (IHN) 144, it is configured to include an accelerator opening degree sensor 146, the control unit (controller) 200.

  The vehicle 1000 according to the present embodiment is provided with motors 108, 110, 112, and 114 for driving the front wheels 100 and 102 and the rear wheels 104 and 106, respectively. Therefore, the driving torque can be controlled by each of the front wheels 100 and 102 and the rear wheels 104 and 106. Accordingly, the yaw rate can be generated by the torque vectoring control by driving each of the front wheels 100 and 102 and the rear wheels 104 and 106 independently of the yaw rate generation by the steering of the front wheels 100 and 102. Steering steering assist can be performed. That is, in the vehicle 1000 according to this embodiment, the turning moment control (hereinafter also referred to as the yaw moment) is controlled by the vehicle body turning angular velocity (hereinafter referred to as the yaw rate), and the turning assist control for assisting the steering is performed.

  The drive of each motor 108, 110, 112, 114 is controlled by controlling the inverters 123, 124, 125, 126 corresponding to the motors 108, 110, 112, 114 based on commands from the control device 200. The The driving force of each motor 108, 110, 112, 114 is transmitted to each of the front wheels 100, 102 and the rear wheels 104, 106 via the gear boxes 116, 118, 120, 122. In a vehicle 1000 capable of independent left and right drive using motors 108, 110, 112, 114 having excellent responsiveness and inverters 123, 124, 125, 126, the turning moment (yaw moment) is controlled by the vehicle body turning angular velocity (yaw rate). And turn assist control for assisting steering steering.

  The power steering mechanism 140 controls the steering angle of the front wheels 100 and 102 by torque control or angle control according to the operation of the steering wheel 130 by the driver. The steering angle sensor 138 detects the steering angle θh input by the driver operating the steering wheel 130. The yaw rate sensor 142 detects the actual yaw rate γ of the vehicle 1000. Wheel speed sensors 127 and 128 detect vehicle speed V of vehicle 1000.

  Note that the present embodiment is not limited to this form, and may be a vehicle in which only the rear wheels 104 and 106 independently generate a driving force. Further, the present embodiment is not limited to torque vectoring based on driving force control, and can also be realized in a 4WS system for controlling the steering angle of the rear wheels.

  FIG. 2 is a schematic diagram for explaining general yaw rate feedback control. The target yaw rate γ_tgt is obtained from the vehicle speed V and the steering angle θh. On the other hand, the actual yaw rate γ is detected by the yaw rate sensor 142. Then, the difference Δγ between the target yaw rate γ_tgt and the actual yaw rate γ is converted into the vehicle body additional moment Mg based on the vehicle specifications, and the rear wheel motor torque instruction values (Frl (left rear wheel), Frr ( Calculate the right rear wheel)). In this way, by feeding back the actual yaw rate γ to the target yaw rate γ_tgt, the vehicle 1000 can be turned according to the target yaw rate γ_tgt.

  Next, the action of the turning assist control will be described in detail with reference to FIGS. FIG. 3 is a diagram illustrating a relationship between a slip angle of a wheel (hereinafter also referred to as a tire) and lateral acceleration.

  As shown in FIG. 3, in the characteristics indicating the relationship between the tire slip angle (slip angle) and the lateral acceleration (hereinafter also referred to as cornering characteristics or tire lateral force characteristics), the lateral acceleration is linear with respect to the slip angle. In the linear region (region where the slip angle is relatively small), the lateral acceleration increases as the slip angle increases. For example, in the planar two-wheel model, it is assumed that the cornering characteristics of the tire are linear, and in the above linear region, the behavior of the model and the actual vehicle approximately match.

  On the other hand, when the slip angle increases to some extent, the cornering characteristic of the tire becomes nonlinear, unlike the two-wheel model. That is, there is a non-linear region where the lateral acceleration becomes nonlinear with respect to the slip angle, and in the non-linear region, the increase rate of the lateral acceleration with respect to the increase rate of the slip angle decreases.

  Thus, when the slip angle increases to some extent, the increase rate of the obtained lateral acceleration decreases, so that the lateral acceleration is likely to be saturated. And when the lateral acceleration of the front wheels is saturated, understeer occurs. Therefore, independent of the generation of the yaw moment due to the steering of the front wheels, by applying the turn assist control that generates the yaw moment in the same direction to the rear wheels of the vehicle, lateral acceleration can be additionally obtained, Saturation is avoided. As a result, understeer is suppressed and the vehicle can turn in response to steering.

FIG. 4 is a characteristic diagram showing the relationship between the tire slip ratio and the longitudinal force. In the characteristics shown in FIG. 4 (hereinafter also referred to as tire longitudinal force characteristics), the longitudinal force increases while the slip ratio increases until the slip ratio increases to some extent. For example, when the longitudinal force is increased to the upper limit of the frictional circle characteristic of the tire, the longitudinal force is saturated. In general, the slip ratio on the horizontal axis in FIG. 4 is calculated by the following equation (1).
Slip rate = (vehicle speed−wheel speed) / vehicle speed (1)

  As shown in FIG. 4, the longitudinal force starts to decrease when the slip ratio increases to some extent. This is because when the slip ratio increases, the frictional circle characteristic of the tire decreases and the allowable amount of longitudinal force decreases. In this state, when the gain of the turn assist control is increased, the longitudinal force characteristic of the tire changes so as to approach the region surrounded by the broken line shown in FIG. 4, that is, the slip ratio increases and the longitudinal force decreases. . On the other hand, when the gain of the turn assist control is decreased, the longitudinal force characteristic of the tire changes so as to approach the region surrounded by the alternate long and short dash line shown in FIG. 4, that is, the slip ratio decreases and the longitudinal force increases. . If the gain of the turn assist control is further reduced, the slip ratio is reduced and the longitudinal force is also reduced.

  Here, on a road surface with a low μ, the frictional circle characteristic of the tire is smaller than that on a road surface with a high μ, so that the allowable amount of longitudinal force and lateral force is reduced. If the gain of the turn assist control is increased in this state, the slip ratio increases, and the frictional circle characteristics of the rear wheel tire are further reduced. Therefore, the allowable amount of lateral force is further reduced without obtaining the longitudinal force, and the lateral force is likely to be saturated. As a result, oversteer is likely to occur, and eventually the vehicle may spin.

  As described above, at the turning limit, the vehicle body slips due to saturation of the tire friction circle, and stability cannot be obtained. Conventionally, stability is ensured by reducing the turning assist gain when slipping or the like occurs exceeding the tire limit. For this reason, control is performed after the tire limit is exceeded, and the vehicle becomes unstable. As a factor, the tire frictional circle characteristics can be attributed to cornering characteristics, longitudinal force characteristics, and vertical load. In addition, if the vertical load changes during turning acceleration / deceleration, the turning capacity of the tire is affected. Accordingly, it is preferable to perform the turning assist control in consideration of the longitudinal force characteristics and the vertical load.

  Therefore, in this embodiment, by predicting the turning limit time, the turning performance and the stability performance are improved without exceeding the limit. Specifically, the vehicle body state is predicted from the current turning state of the vehicle, and when the slip is near the limit value of the occurrence of slip, the gain of the turning assist control is reduced early. In this way, by grasping the turning limit before the occurrence of wheel slip or vehicle body slip and reducing the turning control gain before the occurrence of slip, the behavior of the vehicle can be reliably stabilized.

  When predicting the turning limit time, a turning restoration yaw moment (turning yaw moment) is used. Whether or not the vehicle is in an unstable region such as a spin is predicted from the turning restoration yaw moment, and when the vehicle is in an unstable region, the control gain of the turning assist control is decreased.

  Furthermore, in this embodiment, in addition to the turning restoration yaw moment, the vehicle slip angular velocity is used as a control determination condition, and the threshold value for reducing the turning assist control gain is changed. As a result, the gain of the turn assist control can be surely reduced before the vehicle 1000 starts to slip.

The turning restoring yaw moment is a yaw moment that the vehicle 1000 that is generated by a reaction force that the vehicle body structure and the tire receive from the road surface returns to a straight traveling state with respect to the turning moment that is generated by steering when the vehicle 1000 is turning. This is the force to obtain stability when turning. The turning restoration yaw moment is obtained from the sum of the reverse force of the tire lateral force generated during turning due to the vertical load of the tire and the self-aligning torque of each wheel generated by the vehicle body structure. When longitudinal acceleration or lateral acceleration occurs, the ground contact load of each wheel changes, so the turning restoration yaw moment also changes.

  FIG. 5 is a schematic diagram for explaining the self-aligning torque. FIG. 6 is a characteristic diagram showing the relationship between the slip angle and the self-aligning torque. As shown in FIG. 5, the self-aligning torque Ts is a moment generated around the vertical axis among moments generated when the side slip angle β is generated in the tire. The self-aligning torque Ts is a force that acts in a direction in which the cornering force force P is behind the center of the tire and becomes a pneumatic trail to eliminate the side slip angle β and return straight. As shown in FIG. 6, the self-aligning torque increases as the side slip angle increases, and decreases as the side slip angle further increases. Since the self-aligning torque works as a force that inhibits turning, it is handled with a reverse force (negative value) when calculating the turning moment.

  FIG. 7 is a characteristic diagram showing a map for calculating the turning restoration yaw moment (turning yaw moment) according to the present embodiment. The turning restoration yaw moment map shown in FIG. 7 is determined in advance, and is stable when the vehicle 1000 tries to return straight from turning due to the reaction force received from the road surface under the structure of the vehicle body and the tire friction circle when the vehicle 1000 turns. It shows power. FIG. 7 shows the turning restoration yaw moment corresponding to the vehicle slip angle for each of the plurality of tire steering angles δ. As shown in FIG. 7, when the tire rudder angle δ = 4 and the vehicle body slip angle is 2 deg, a turning restoring yaw moment of about −380 kgf · m is generated. This is the value of the turning restoring yaw moment that works to stabilize the vehicle body 1000. The smaller the value of the turn restoring yaw moment, the greater the force that prevents the vehicle 1000 from turning. On the other hand, when the turning restoration yaw moment is 0 or more (a positive value), it becomes a moment that promotes turning. Since the tire steering angle is included in the parameters of the map in FIG. 7, the characteristics of the lateral acceleration are reflected in the map. On the other hand, a change in longitudinal acceleration requires a map for each setting. For this reason, the map shown in FIG. 7 is set for each different longitudinal acceleration. In actual control, the longitudinal acceleration is owned by several points, and intermediate values are applied by interpolation.

  First, at the time of turning assist, the turning restoration yaw moment is obtained from the turning restoration yaw moment map of FIG. The turning restoration yaw moment has an opposite sign to the turning yaw moment by the motors 108, 110, 112, and 114. If the turning restoration yaw moment is a negative value, the turning restoration yaw moment acts as a force that inhibits turning. On the other hand, as shown in FIG. 7, when the vehicle slip angle β increases, the value of the turning recovery yaw moment increases from the minus direction to the plus direction due to the frictional circle characteristics of the tire, and the turning moment increases in the direction that promotes turning. . As a result, the turning of the vehicle 1000 is promoted, and the vehicle 1000 may spin when turning.

  In the present embodiment, when the vehicle slip angle is increased from the current state based on the actual value of the vehicle slip angle, the steering angle θh, and the tire friction circle, the motor 108, The turning assist control gain by 110, 112, 114 is decreased. Accordingly, in the tire friction circle, the tire longitudinal force is reduced and the tire lateral force is increased, so that both turning performance and stability performance during turning can be achieved. Thus, the vehicle stability during turning can be improved by predicting the turning limit based on the turning restoring moment and decreasing the control amount of the turning assist control to increase the share of the tire lateral force. If the vehicle 1000 is in a stable range, the turning moment is assisted by left and right braking / driving force control by driving the motors 108, 110, 112, and 114 in order to further improve the turning performance.

  In the present embodiment, the correction unit that corrects the vehicle body additional moment based on the turning restoration yaw moment can include a turning assist control gain calculation unit 234 and a multiplication unit 236.

  FIG. 8 is a diagram showing the relationship between the longitudinal force and lateral force of the rear wheels. With reference to FIG. 8, the stabilization of the behavior of the vehicle 1000 according to the present embodiment will be described in detail.

  In the characteristic indicating the relationship between the longitudinal force and the lateral force of the rear wheels 106 and 108 (the frictional circle characteristic of the tire), for example, the road surface state is high μ, and before the gain of the turning assist control is decreased, the characteristic shown in FIG. Since the longitudinal force is generated up to the arrow A51 of the longitudinal axis shown in the left figure, the width of the arrow A52 of the lateral axis is an allowable amount of lateral force. In the case of high μ, as indicated by the solid line in the left diagram of FIG. 8, the friction circle C1 is large, so that the lateral force does not saturate even when the longitudinal force is sufficiently used. When the road surface becomes low μ in this state, the friction circle of the tire is in a state of a broken line C2, and the allowable lateral force is saturated, so that oversteer occurs. However, in this embodiment, since the gain of the turning assist control is reduced before the road surface becomes low μ, as shown by an arrow A53 in the left diagram of FIG. Increases (arrow A54). Therefore, since the slip of the rear wheels 106 and 108 in the lateral direction is suppressed, oversteer is not generated, and the behavior of the vehicle 1000 is stabilized.

  Thereafter, when the road surface returns to high μ, the tire friction circle returns from C2 to C3 to C1 in the right diagram of FIG. Therefore, by increasing the gain of the turn assist control and increasing the longitudinal force as indicated by arrows A55, A56, and A57, the longitudinal force of the tire can be increased to the solid friction circle C1.

  FIG. 9 is a schematic diagram showing in detail the configuration of the control device 200 according to the present embodiment and its periphery. The control device 200 includes an in-vehicle sensor 202, a target yaw rate calculation unit 204, a vehicle yaw rate calculation unit (vehicle model) 206, a yaw rate F / B calculation unit 208, subtraction units 210 and 212, a weighting gain calculation unit 220, and an actual vehicle slip angle calculation. Unit 224, vehicle body behavior prediction unit (turning restoration yaw moment calculation unit) 226, vehicle body slip angular velocity calculation unit 222, turn assist control gain calculation unit 234, vehicle body additional moment calculation unit 232, multiplication unit 236, motor required torque calculation unit 238, It is comprised.

  In FIG. 9, the in-vehicle sensor 202 includes the wheel speed sensors 127 and 128, the longitudinal acceleration sensor 132, the lateral acceleration sensor 134, the steering angle sensor 138, the yaw rate sensor 142, and the accelerator opening sensor 146 described above. The steering angle sensor 138 detects the steering angle θh of the steering wheel 130. The yaw rate sensor 142 detects the actual yaw rate γ of the vehicle 1000, and the wheel speed sensors 127 and 128 detect the vehicle speed (vehicle speed) V. The longitudinal acceleration sensor 132 detects the longitudinal acceleration Gx of the vehicle 1000. Lateral acceleration sensor 134 detects lateral acceleration Gy of vehicle 1000.

The target yaw rate calculation unit 204 calculates a target yaw rate γ_tgt based on the steering angle θh and the vehicle speed V. Specifically, the target yaw rate calculation unit 204 calculates a target yaw rate γ_tgt from the following equation (2) that represents a general two-wheel model. The target yaw rate γ_tgt is calculated by substituting the value calculated from Expression (3) and Expression (4) for the right side of Expression (2). The calculated target yaw rate γ_tgt is input to the subtraction unit 210.

Note that the variables, constants, and operators in the equations (2) to (4) are as follows.
Ganma_tgt: target yaw rate [theta] h: steering angle V: vehicle speed T: When the vehicle constant S: Laplace operator N: steering gear ratio l: vehicle wheel base l _f: distance from the vehicle center of gravity to the front wheel center l _r: vehicle Distance from center of gravity to center of rear wheel m: Vehicle weight K _ftgt : Target cornering power (front wheel)
K _rtgt : Target cornering power (rear wheel)

As described above, the target yaw rate γ_tgt is calculated from the equation (2) using the vehicle speed V and the steering angle θh as variables. The constant A _tgt in the equation (3) is a constant representing the characteristics of the vehicle, and is obtained from the equation (4).

The vehicle yaw rate calculation unit 206 calculates the yaw rate model value γ_clc from the following equation for calculating the vehicle yaw rate. Specifically, the yaw rate model value γ_clc is obtained by substituting the vehicle speed V and the steering angle θh into the following formulas (5) and (6) and solving the formulas (5) and (6) simultaneously. (Γ in Equations (5) and (6)) is calculated. Equation (5), in equation (6), _{K f} is the cornering power (front), the _{K r} represents a cornering power (rear). In Expression (4), the target yaw rate γ_tgt is obtained from the yaw rate model value γ_clc by using target cornering powers K _ftgt and K _rtgt different from the cornering powers K _f and K _r in Expression (5) and Expression (6). To improve the turning performance. The yaw rate model value γ_clc is output to the yaw rate F / B calculation unit 208. In addition, the yaw rate model value γ_clc is input to the subtraction unit 212.

  On the other hand, the actual yaw rate γ (hereinafter referred to as the actual yaw rate γ_sens) of the vehicle 1000 detected by the yaw rate sensor 142 is input to the subtracting unit 212. The subtracting unit 212 subtracts the yaw rate model value γ_clc from the actual yaw rate γ_sens to obtain a difference γ_diff between the actual yaw rate γ_sens and the yaw rate model value γ_clc. The difference γ_diff is input to the weighting gain calculator 220.

  The weighting gain calculator 220 calculates the weighting gain a based on the difference γ_diff between the actual yaw rate γ_sens and the yaw rate model value γ_clc.

The yaw rate F / B calculation unit 208 receives the yaw rate model value γ_clc, the actual yaw rate γ_sens, and the weighting gain a. The yaw rate F / B calculation unit 208 calculates the feedback yaw rate γ_F / B by weighting the yaw rate model value γ_clc and the actual yaw rate γ_sens by the weighting gain a based on the following equation (7). The calculated feedback yaw rate γ_F / B is output to the subtraction unit 210.
γ_F / B = a × γ_clc + (1−a) × γ_sens (7)

  FIG. 10 is a schematic diagram showing a gain map when the weighting gain calculation unit 220 calculates the weighting gain a. As shown in FIG. 10, the value of the weighting gain a varies between 0 and 1 according to the reliability of the vehicle model. A difference (deviation) γ_diff between the yaw rate model value γ_clc and the actual yaw rate γ_sens is used as an index for improving the reliability of the vehicle model. As shown in FIG. 10, the gain map is set so that the value of the weighting gain a increases as the absolute value of the difference γ_diff decreases. The weighting gain calculation unit 220 performs the map processing of FIG. 10 on the difference γ_diff and calculates a weighting gain a corresponding to the reliability of the vehicle model.

  In FIG. 10, the weighting gain a is a value from 0 to 1 (0 ≦ a <1). When −0.05 [rad / s] ≦ γ_diff ≦ 0.05 [rad / s], the weighting gain a is 1 (a = 1).

  When 0.05 <γ_diff, or when γ_diff <−0.05, the weighting gain a is set to 0 (a = 0).

When 0.05 [rad / s] <γ_diff <0.1 [rad / s], the weighting gain a is calculated by the following equation.
a = −20 × γ_diff + 2

When −0.1 [rad / s] ≦ γ_diff <−0.05 [rad / s], the weighting gain a is calculated by the following equation.
a = + 20 × γ_diff + 2

  A region A1 of the gain map shown in FIG. 10 is a region where the difference γ_diff approaches 0, a region where the S / N ratio of the actual yaw rate γ_sens is small, and a region where the tire characteristics are linear (dry road surface). The reliability of the yaw rate model value γ_clc calculated from the calculation unit 206 is high. For this reason, the feedback yaw rate γ_F / B is calculated with the weighting gain a = 1 and the distribution of the yaw rate model value γ_clc as 100% according to the equation (7). Thereby, the influence of the noise of the yaw rate sensor 142 included in the yaw rate γ_sens can be suppressed, and the sensor noise can be excluded from the feedback yaw rate γ_F / B. Therefore, it is possible to suppress the vibration of the vehicle 1000 and improve the riding comfort.

  Here, as a factor causing a difference between the actual yaw rate γ and the yaw rate model value γ_clc obtained from the vehicle model, the dynamic characteristics of the tire shown in FIG. 3 can be cited. The planar two-wheel model described above assumes a region in which the relationship between the tire slip angle and the lateral acceleration (tire cornering characteristics) is linear. In this linear region, the actual yaw rate γ and the yaw rate model value γ_clc are substantially equal. Match. In the characteristic indicating the relationship between the slip angle and the lateral acceleration shown in FIG. 3, in the linear region where the lateral acceleration is linear with respect to the slip angle (region where the steering speed is relatively slow), the influence of the sensor noise of the yaw rate sensor 142. Will occur. Therefore, the yaw rate model value γ_clc is used in this region.

  On the other hand, in the region where the cornering characteristic of the tire is nonlinear, the yaw rate and lateral acceleration of the actual vehicle become nonlinear with respect to the steering angle and slip angle, and the two-wheeled model and the yaw rate sensed by the actual vehicle deviate. In such a transient non-linear region, noise does not occur due to the sensor characteristics of the yaw rate sensor 142, so the actual yaw rate γ can be used. The non-linear region corresponds to, for example, the timing for switching the steering. When the actual yaw rate γ exceeds the yaw rate model value γ_clc, it corresponds to a non-linear region and is not affected by sensor noise. Therefore, by using the actual yaw rate γ, control based on the true value is possible. If a model that takes into account tire nonlinearity is used, control based on the yaw rate becomes complicated, but according to the present embodiment, the reliability of the yaw rate model value γ_clc can be easily determined based on the difference γ_diff. In the non-linear region, the actual yaw rate γ can be increased and used. Further, a region that is hardly affected by the dynamic characteristics of the tire can be dealt with by the yaw rate model value γ_clc.

  Further, the gain map area A2 shown in FIG. 10 is an area where the difference γ_diff is large, which corresponds to a wet road surface, a snow road, a turn with a high G, and the like. It is an area. In this region, the reliability of the yaw rate model value γ_clc calculated from the vehicle yaw rate calculation unit 206 is reduced, and the difference γ_diff is increased. Therefore, the feedback yaw rate γ_F / B is calculated with the weighting gain a = 0 and the distribution of the actual yaw rate γ_sens as 100% according to the equation (7). Thus, feedback accuracy is ensured based on the actual yaw rate γ_sens, and feedback control of the yaw rate reflecting the behavior of the actual vehicle is performed. Therefore, the turning of the vehicle 1000 can be optimally controlled based on the actual yaw rate γ_sens. Further, since the tire is in a slipping region, even if the signal of the yaw rate sensor 142 is affected by noise, the driver does not feel it as vibration of the vehicle 1000, and a decrease in riding comfort can be suppressed. Regarding the setting of the low μ region A2 shown in FIG. 10, the region where the weighting gain κ = 0 may be determined from the design requirements, and the steering stability performance when the vehicle 1000 actually travels on the low μ road surface, You may decide experimentally from comfort etc.

  Further, the gain map area A3 shown in FIG. 10 is an area (nonlinear area) in which a transition from a linear area to a limit area is performed, and the yaw rate model value γ_clc is also considered in consideration of the tire characteristics of the actual vehicle 1000 as necessary. And the distribution (weighting gain a) of the actual yaw rate γ_sens are changed linearly. In the transition from the region A1 (high μ region) to the region A2 (low μ region) or in the region transitioning from the region A2 (low μ region) to the region A1 (high μ region), the torque associated with the sudden change in the weighting gain a In order to suppress fluctuations and fluctuations in the yaw rate, the weighting gain a is calculated by linear interpolation.

  A gain map region A4 shown in FIG. 10 corresponds to the case where the actual yaw rate γ_sens is larger than the yaw rate model value γ_clc. For example, when an incorrect parameter is input to the vehicle yaw rate calculation unit 206 and the yaw rate model value γ_clc is erroneously calculated, control can be performed using the actual yaw rate γ_sens based on the map of the region A4. It should be noted that the range of the weighting gain a is not limited to 0 to 1, and the configuration of the present invention can be changed so that an arbitrary value can be taken as long as the range is established as vehicle control. Enter into a possible category.

The subtraction unit 210 subtracts the feedback yaw rate γ_F / B from the control target yaw rate γ_tgt input from the target yaw rate calculation unit 204 to obtain a difference Δγ between the control target yaw rate γ_tgt and the feedback yaw rate γ_F / B. That is, the difference Δγ is calculated from the following equation (8).
Δγ = γ_Tgt−γ_F / B (8)
The difference Δγ is input to the vehicle body additional moment calculation unit 232 as a yaw rate correction amount.

  The vehicle body additional moment calculation unit 232 calculates the vehicle body additional moment Mg based on the input difference Δγ so that the difference Δγ becomes 0, that is, the control target yaw rate γ_tgt matches the feedback yaw rate γ_F / B. To do. Specifically, the vehicle body additional moment Mg is calculated from the following equation (9). As a result, the vehicle body additional moment Mg necessary for turning at the center position of the vehicle 1000 is obtained. A turning moment is added to the vehicle 1000 based on the vehicle body additional moment Mg.

The actual vehicle slip angle calculation unit 224 calculates the actual vehicle slip angle Slip_ang_real based on the actual yaw rate γ_sens, the lateral acceleration Gy, and the vehicle speed V. Specifically, the actual vehicle slip angle calculation unit 224 calculates the actual vehicle slip angle Slip_ang_real (actual vehicle slip angle βreal) from the following equation (10). Note that a value detected by the lateral acceleration sensor 134 is used as the lateral acceleration Gy. The calculated actual vehicle slip angle Slip_ang_real is input to the vehicle body behavior prediction unit 226.
Slip_ang_real = d (Gy / V−γ_sens) / dt (10)

  The vehicle behavior prediction unit 226 receives the longitudinal acceleration Gx detected by the longitudinal acceleration sensor 132 and the steering angle θh detected by the steering angle sensor 138. The vehicle behavior prediction unit 226 calculates a turning restoration yaw moment βm from the map of FIG. 7 based on the input actual vehicle slip angle βreal, tire steering angle δ, and longitudinal acceleration Gx. The tire steering angle δ is obtained by dividing the steering angle θh by the steering gear ratio N.

  The vehicle slip angular velocity calculation unit 222 calculates a vehicle slip angular velocity β′real, which is a change amount per unit time of the actual vehicle slip angle βreal based on the actual vehicle slip angle βreal.

  The turning assist control gain calculation unit 234 calculates a turning assist gain βG based on the turning restoration yaw moment βm and the vehicle slip angular velocity β′real. The turning assist gain βG is basically determined based on the turning restoration yaw moment βm obtained by applying the actual vehicle slip angle βreal to the map of FIG. On the other hand, since the actual vehicle slip angle βreal does not have a function of time, the turning assist control gain calculating unit 234 adds the vehicle body slip angular velocity in addition to the turning restoration yaw moment βm in order to improve stability against transient vehicle behavior. A turning assist gain βG is calculated based on β′real. As a result, the stability of the vehicle 1000 can be greatly increased in both steady motion and transient motion. A method for calculating the turning assist gain βG will be described in detail later.

  The turning assist gain βG calculated by the turning assist control gain calculation unit 234 is input to the multiplication unit 236. The multiplication unit 236 also receives the vehicle body additional moment Mg calculated by the vehicle body additional moment calculation unit 232. The multiplier 236 multiplies the vehicle body additional moment Mg by the turning assist gain βG to calculate a correction value Mg ′ for the vehicle body additional moment Mg.

  The correction value Mg ′ is input to the motor required torque calculation unit 238. The motor required torque calculation unit 238 calculates ΔTv from the following equation (11) in order to convert the moment into torque using the correction value Mg ′ obtained by multiplying the vehicle body additional moment Mg by the turning assist gain βG. Then, the motor required torque calculation unit 238 calculates the additional torque Tvmot from the following equation (12).

  In Formula (11), TrdR is the tread width of the rear wheels 104 and 106. Further, TireR is a tire radius of the front wheels 100 and 102 and the rear wheels 104 and 106, and Gratio is a gear ratio of the gear boxes 120 and 122 of the rear wheels 104 and 106. The correction value Mg ′ of the vehicle body additional moment Mg at the center position of the vehicle 1000 is converted into the motor torque ΔTv of the rear wheels 104 and 106 by Expression (11). Then, the respective motor torques of the rear wheels 104 and 106 necessary for generating the correction value Mg ′ are obtained from the equation (12).

By the way, the driving force of the front wheels 100 and 102 and the rear wheels 104 and 106 is determined by the motor torque instruction value reqTq that is determined from the driver's required driving force (accelerator pedal opening) when the vehicle 1000 is traveling straight. Here, the motor torque instruction value reqTq is calculated from the following equation (13).
reqTq = reqF * TireR * Gratio (13)
In Expression (13), reqF is a required driving force determined from the opening of the accelerator pedal. The opening degree of the accelerator pedal is detected by an accelerator opening degree sensor 146.

  When the vehicle 1000 travels straight, the driving force of each of the four motors 108, 110, 112, 114 that drives the front wheels 100, 102 and the rear wheels 104, 106 is a motor torque instruction value reqTq based on the driver's required driving force reqF. The value is divided into four equal parts (= reqTq / 4). On the other hand, when the vehicle 1000 turns, an additional torque Tvmot based on the vehicle body additional moment Mg ′ calculated from the equation (12) is added to the motor torque command value reqTq of the rear wheels 104 and 106 by torque vectoring control. Since the additional torque Tvmot based on the vehicle body additional moment Mg ′ is a couple, in the case of a right turn, the motor torque instruction value of the left rear wheel 104 is set to the motor torque instruction value reqTq / 4 at the time of straight traveling by adding the additional torque Tvmot. The motor torque instruction value of the right rear wheel 106 is a value obtained by subtracting the additional torque Tvmot from the motor torque instruction value reqTq / 4 when traveling straight. Similarly, in the case of a left turn, the motor torque instruction value of the right rear wheel 106 is a value obtained by adding the additional torque Tvmot to the motor torque instruction value reqTq / 4 when traveling straight, and the motor torque instruction value of the left rear wheel 104 Is a value obtained by subtracting the additional torque Tvmot from the motor torque instruction value reqTq / 4 during straight travel.

Therefore, the motor torque instruction values of the motors 108, 110, 112, and 114 at the time of turning can be expressed by the following equations (14) to (17). The motor required torque calculation unit 228 calculates motor torque instruction values TqmotFl, TqmotFr, TqmotRl, and TqmotRr for each of the motors 108, 110, 112, and 114 based on the equations (14) to (17).
TqmotFl (motor torque instruction value of the left front wheel) = reqTq / 4 (14)
TqmotFr (motor torque instruction value of the right front wheel) = reqTq / 4 (15)
TqmotRl (Left rear wheel motor torque instruction value)
= ReqTq / 4- (± Tvmot) (16)
TqmotRr (Right rear wheel motor torque instruction value)
= ReqTq / 4 + (± Tvmot) (17)
The sign of the additional torque Tvmot is set according to the turning direction.

  Next, processing performed by the control device 200 according to the present embodiment will be described. FIG. 11 is a flowchart showing the overall processing of this embodiment. First, in step S100, it is determined whether or not an ignition key (ignition SW) is on. If the ignition key is turned on, the process proceeds to step S102. If the ignition key is not turned on, the process waits in step S100.

  In step S102, it is determined whether or not the inhibitor position sensor (IHN) 144 indicates the position of P (parking) or N (neutral). If it is the position of P (parking) or N (neutral), step S104 is performed. Proceed to If it is determined in step S102 that the position is not P (parking) or N (neutral), the process proceeds to step S106, where it is determined whether or not the ignition key is turned on. If the ignition key is turned on, the process returns to step S102. . If the ignition key is off in step S106, the process proceeds to step S108, the vehicle activation process is terminated, and the process returns to step S100.

  In step S104, the starting process of the vehicle 1000 is performed, and in the next step S110, it is determined whether or not the inhibitor position sensor (IHN) 144 indicates the position of D (drive) or R (reverse). When the inhibitor position sensor (IHN) 144 indicates the position of D (drive) or R (reverse), the process proceeds to step S112, and the travel control process is started. On the other hand, if the inhibitor position sensor (IHN) 144 does not indicate the position of D (drive) or R (reverse) in step S110, the process proceeds to step S113 to determine whether or not the ignition key is turned on. If the key is on, the process returns to step S110. If the ignition key is off in step S113, the process proceeds to step S108, the vehicle activation process is terminated, and the process returns to step S100.

  After step S112, the process proceeds to step S114, and the operation amount (accelerator opening) of the accelerator pedal by the driver is detected from the detection value of the accelerator opening sensor 146. In the next step S115, it is determined whether or not the operation amount of the accelerator pedal is 0.1 or more. If the operation amount is 0.1 or more, the process proceeds to step S116. In step S116, the required driving force reqF is calculated based on the operation amount of the accelerator pedal. The required driving force reqF can be calculated based on, for example, a map that defines the relationship between the accelerator opening and the required driving force reqF. On the other hand, when the operation amount of the accelerator pedal is less than 0.1, the process proceeds to step S118, and regenerative braking control of each motor 108, 110, 112, 114 is performed.

  After steps S116 and S118, the process proceeds to step S120. In step S120, it is determined whether or not the absolute value of the steering angle θh detected by the steering angle sensor 138 is 1 [deg] or more. If the absolute value of the steering angle θh is 1 [deg] or more, Proceed to step S122. In step S122, the additional torque Tvmot is calculated by the above-described method, and feedback control to the target moment γ_Tgt is performed based on the additional torque Tvmot. Therefore, in the next step S124, the motor torque instruction values of the motors 108, 110, 112, 114 are calculated from the equations (14) to (17) based on the additional torque Tvmot, and the motors 108, 110, 112 are calculated. , 114 is instructed to output. In the next step S126, the accelerations Gx and Gy of the vehicle 1000 are detected by the longitudinal acceleration sensor 132 and the lateral acceleration sensor 134. After step S126, the process returns to step S114.

  Next, main processes of the process of FIG. 11 will be described in detail. FIG. 12 is a flowchart showing the process of step S122 of FIG. Here, FIG. 12 is a flowchart illustrating a process in which the weighting gain calculation unit 220 calculates the weighting gain a. The process of FIG. 12 functions as a process of removing noise from the yaw rate sensor 142 by calculating the feedback yaw rate γ_F / B by allocating the actual yaw rate γ_sens and the yaw rate model value γ_clc based on the weighting gain a. First, in step S200, an actual yaw rate γ_sens and a yaw rate model value γ_clc are acquired. In the next step S201, a difference γ_diff between the actual yaw rate γ_sens and the yaw rate model value γ_clc is calculated. In the next step S202, the weighting coefficient a is calculated based on the gain map of FIG. In the next step S204, the feedback yaw rate γ_F / B is calculated based on the above-described equation (7). The calculated feedback yaw rate γ_F / B is used for calculating the difference Δγ in step S224 of FIG.

  FIG. 13 is a flowchart illustrating a process in which the vehicle yaw rate calculation unit 206 calculates the yaw rate model value γ_clc. First, in step S210, the steering angle θh and the vehicle speed V are acquired. In the next step S212, the yaw rate model value γ_clc is calculated by simultaneously solving the equations (5) and (6). The calculated yaw rate model value γ_clc is used for calculating the feedback yaw rate γ_F / B in step S204 of FIG.

  FIG. 14 is a flowchart showing a process for calculating the additional torque Tvmot. First, in step S220, the target yaw rate calculation unit 204 acquires the steering angle θh and the vehicle speed V. In the next step S222, the target yaw rate γ_Tgt is calculated from the equations (2) to (4) based on the steering angle θh and the vehicle speed V. In the next step S224, a difference Δγ between the control target yaw rate γ_Tgt and the feedback yaw rate γ_F / B is calculated based on the equation (7). In the next step S226, the vehicle body additional moment Mg is calculated from the equation (9).

  In the next step S228, the turning assist control gain calculating unit 234 calculates the turning assist gain βG. In the next step S230, ΔTv is calculated based on the equation (11), and the additional torque Tvmot is calculated based on the equation (12). Based on the calculated additional torque Tvmot, a motor torque instruction value for each wheel is calculated in step S124 of FIG.

  FIG. 15 is a flowchart showing a process for calculating the turning assist gain βG. First, in step S240, the longitudinal acceleration Gx, the lateral acceleration Gy, the vehicle speed V, the actual yaw rate γ_sens, and the tire steering angle δ are acquired as input values. In the next step S242, the actual vehicle slip angle calculation unit 224 calculates the actual vehicle slip angle βreal from equation (10).

  In the next step S244, the vehicle behavior prediction unit 226 calculates a turning restoration yaw moment βm from the map of FIG. 7 based on the actual vehicle slip angle βreal, tire steering δ, and longitudinal acceleration Gx. As described above, the map of FIG. 7 is prepared in advance according to the value of the longitudinal acceleration Gx. For example, the vehicle behavior prediction unit 226 first selects a corresponding map based on the longitudinal acceleration Gx, and applies the actual vehicle slip angle βreal and the tire rudder angle δ to the selected map to calculate the turning restoration yaw moment βm.

  In the next step S246, the vehicle slip angular velocity calculation unit 222 calculates the vehicle slip angular velocity β'real. In the next step S248, it is determined whether or not the absolute value of the vehicle slip angular velocity β′real is 6 deg / s or less. If | β′real | ≦ 6 deg / s, the process proceeds to step S250. In this case, since | β′real | ≦ 6 deg / s, the amount of change in the vehicle body slip angle βreal per unit time is relatively small, and it is considered that the turning of the vehicle 1000 is in a steady motion. Accordingly, in the subsequent processing, processing corresponding to the steady movement of the vehicle 1000 is performed.

  In step S250, it is determined whether or not the turning restoring yaw moment βm is −2000 Nm or less. If βm ≦ −2000 Nm, the process proceeds to step S252, and the turning assist gain βG is set to 1.

On the other hand, if βm> −2000 Nm in step S250, the process proceeds to step S254, and the turning assist gain βG is calculated from the following equation (18).
βG = −0.00067 * βm − 0.333 (18)

  FIG. 16 is a characteristic diagram showing the turning assist gain βG calculated in steps S252 and S254. As shown in FIG. 16, in the processing corresponding to the steady movement of the vehicle 1000, the turning assist gain βG increases the value of the turning restoring yaw moment βm when the value of the turning restoring yaw moment βm is larger than −2000 Nm. When the value of the turning restoring yaw moment βm approaches zero, the turning assist gain βG is set to zero. Accordingly, the turning assist torque can be reduced as the value of the turning restoration yaw moment βm increases. Note that the minimum value of the turning assist gain βG is not 0, and may be a value larger than 0, such as 0.1.

  If | β′real |> 6 deg / s in step S248, the process proceeds to step S256. In this case, since | β′real |> 6 deg / s, the amount of change in the vehicle slip angle βreal per unit time is relatively large, and it is considered that the turning of the vehicle 1000 is making a transitional motion. Accordingly, in the subsequent processing, processing corresponding to the transitional movement of the vehicle 1000 is performed.

In step S256, it is determined whether or not the turn restoring yaw moment βm is equal to or greater than −4000 Nm. If βm ≧ −4000 Nm, the process proceeds to step S258, and the turn assist gain βG is calculated from the following equation (19).
βG = −0.00025 * βm − 0.143 (19)

Figure 17 is a characteristic diagram showing a turning assist gain βG calculated in step S 258. As shown in FIG. 17, in the process corresponding to the transient movement of the vehicle 1000, the turning assist gain βG increases when the value of the turning restoration yaw moment βm is larger than −4000 Nm. When the value of the turning restoring yaw moment βm approaches zero, the turning assist gain βG is set to zero. Therefore, compared with FIG. 16, even if the turning restoration yaw moment βm shows a smaller value of −2000 or less, if the turning restoration yaw moment βm is −4000 Nm or more, the turning assist gain βG is 1. It becomes the following values. Therefore, as compared with the control corresponding to the steady movement, the value of the turning assist gain βG is decreased in the control corresponding to the transient movement even if the turning restoration yaw moment βm is a smaller value. Thereby, in the situation where the slip of the vehicle 1000 may occur, the turning assist torque can be reduced from an earlier stage, and the lateral force of the tire can be reliably ensured.

  On the other hand, if βm <−4000Nm in step S256, the process proceeds to step S254, and the turning assist gain βG is calculated from the equation (18).

  After steps S252, S254, and S258, the process proceeds to step S260. In step S260, the value of the turning assist gain βG is set in the range of 0 to 1 by setting the turning assist gain βG to the value set in steps S252, S254, and S258.

  As described above, according to the processing of FIG. 15, the value of the turning recovery yaw moment βm can be optimally controlled within the range of 0 to 1 based on the actual vehicle slip angle βreal and the vehicle slip angular velocity β′real. it can. As a result, the value of the turning assist gain βG can be reduced from the stage before the vehicle 1000 slips, so that the lateral force of the tire can be reliably ensured and the vehicle 1000 can be prevented from slipping. The behavior of the vehicle 1000 can be stabilized.

Hereinafter, an example of a method for creating the map shown in FIG. 7 will be described. The turning restoration yaw moment βm can be calculated from the following equation ( 20 ).
βm = −lf * Fyf + lr * Fyr + (TSAfl + TSAfr + TSArl + TSArr) (20)

The variables, constants, and operators in equation (20) are as follows.
lf: Distance between front wheel axis and center of gravity lr: Distance between rear wheel axis and center of gravity Fyf: Front wheel lateral force (Fyf = Fyfl (left front wheel) + Fyfr (right front wheel))
Fyr: Rear wheel lateral force (Fyr = Fyrl (left rear wheel) + Fyrr (right rear wheel))
TSAfl: Self-aligning torque (Fl)
TSAfr: Self-aligning torque (Fr)
TSArl: Self-aligning torque (Rl)
TSArr: Self-aligning torque (Rr)

  In the equation (20), self-aligning torques TSAfl, TSAfr, TSArl, and TSArr are calculated from vehicle specifications. Further, the front wheel lateral force Fyf and the rear wheel lateral force Fyr are determined from the tire friction circle based on the ground load of the front wheel and the rear wheel. In the calculation of the ground load, the acceleration / deceleration of the vehicle 1000 affects.

In order to calculate the front wheel lateral force Fyf, the lateral force Fyfl of the left front wheel and the lateral force Fyfr of the right front wheel are calculated. Further, in order to calculate the rear wheel lateral force Fyr, the left rear wheel lateral force Fyr and the right rear wheel lateral force Fyrr are calculated. Hereinafter, a method for calculating the lateral force Fyfl of the left front wheel will be described. The lateral force Fyfr of the right front wheel, the lateral force Fyrl of the left rear wheel, and the lateral force Fyrr of the right rear wheel can be calculated in the same manner as the lateral force Fyfl of the left front wheel.
Fyfl = Fy'fl + Sv
Fy′fl = D * sin (C * arctan (Bx−E * (Bx−arctan (Bx)))
x = β + Sh
C = a ₀
μ = a ₁ * Fzfl + a ₂
BCD = (1−a ₅ * | γ |) (a ₃ * sin (2 * arctan (Fzfl / a ₄ )))
B = BCD / (C * D)
D = Fzfl * μ
E = a ₆ Fzfl + a ₇
Sh = a ₈ * γ + a ₉ * Fzfl + a ₁₀
Sv = a ₁₁ Fzfl * γ + a ₁₂ Fzfl + a ₁₃
Here, a _{1 to} a ₁₃ are tire measurement data.
Fzfl is the vertical load on the left front wheel.
Similarly, Fyfr, Fyrl, Fyrr can be calculated.

  In the above calculation, the vertical load Fzfl of the left front wheel is used. A calculation method of the vertical load Fz (the vertical load Fzfl of the left front wheel) will be described below.

Changes due to load movement in the front and rear and right and left directions (front and rear load movement amount ΔWx) are calculated.
Gx: longitudinal acceleration Gy: lateral acceleration

Front / rear load travel ΔWx
ΔWx = m * Gx * Hg / L
m: Mass Hg: Center of gravity height L: Wheel base

Lateral load movement ΔWyf (front), ΔWyr (rear)
ΔWyf = m * Gy {Hs / (1 + Kr / KRf−m * Hs / KRf) + lr * Hf / L} / lf
ΔWyr = m * Gy {Hs / (1 + Kf / KRr−m * Hs / KRr) + lf * Hr / L} / lr
Hs: Center of gravity height to roll center axis distance Hf: Front roll center height (front roll center ground distance)
Hr: Rear roll center height (rear distance between rear roll centers)
KRf: front roll center rigidity KRr: rear roll center rigidity lf: distance from the vehicle center of gravity to the front wheel center lr: distance from the vehicle center of gravity to the rear wheel center

The vertical load Fzfl of the left front wheel can be calculated based on the forward / backward load movement amount ΔWx and the lateral load movements ΔWyf (front) and ΔWyr (rear). Similarly, the vertical load Fzfr on the right front wheel, the vertical load Fzrl on the left rear wheel, and the vertical load Fzrr on the right rear wheel are also based on the longitudinal load movement amount ΔWx and the lateral load movements ΔWyf (front) and ΔWyr (rear). Can be calculated. Accordingly, since the front wheel lateral force Fyf and the rear wheel lateral force Fyr are obtained, the map of the turning restoration yaw moment βm shown in FIG. 7 can be calculated from the equation ( 20 ).

  FIG. 18A to FIG. 18B and FIG. 19A to FIG. 19B are characteristic diagrams for explaining the effects when the control according to the present embodiment is performed. 18A to 18B show a case where the control according to the present embodiment is not performed for comparison. On the other hand, FIG. 19A-FIG. 19B have shown the case where the control which concerns on this embodiment is performed. Here, FIGS. 18A to 18B and FIGS. 19A to 19B are comparisons of vehicle behavior in the case where the vehicle speed is 80 km / h and the steering at 90 degrees is performed as the steering.

  18A and 19A show the rotational speeds of the front wheels 100 and 102 and the rear wheels 104 and 106 in comparison with the motor torque, respectively. Wfl is the left front wheel, Wfr is the right front wheel, Wrl is the left rear wheel, and Wrr is the rotation number of the right rear wheel. Further, TirecapFFz indicates the torque of the front tire, and TirecapRFz indicates the torque of the rear tire.

  In the region R1 of FIG. 18A, it can be seen that the rotation speed (Wrr) of the rear tire is increased. In the region R2, it can be seen that the torque of the rear tire is 0 or less and exceeds the friction circle limit. As described above, in the state shown in FIG. 18A, the turning assist control gain is increased even when the vehicle slip angular velocity is high. As a result, the rear tire exceeds the tire friction circle limit and the tire is idling.

  On the other hand, in the control according to the present embodiment shown in FIG. 19A, as shown in the region R2, the turning assist control is suppressed at the frictional circle limit of the rear tire. ) Does not occur.

18B and 19B show the transition of the turning restoration yaw moment and the turning assist gain βG in comparison. As shown in FIG. 19B, in this embodiment, the turning assist gain βG is reduced to 1 or less. On the other hand, in the example shown in FIG. 18B, the value 1.0 is maintained for the turning assist gain βG. For this reason, in the present embodiment shown in FIG. 19B, it can be seen that in the region R3, the turning restoring yaw moment is reduced as compared with FIG. 18B as the turning assist gain βG decreases. As described above, when the turning restoring moment increases with a positive value, the turning assist torque increases. As shown in FIG. 19B, it is possible to reduce the turning assist torque by reducing the turning assist gain βG .

  As described above, it is possible to reduce the turning restoring moment by reducing the gain of the turning assist torque (turning assist gain βG). Moreover, since generation | occurrence | production of a surplus torque can be suppressed, it becomes possible to suppress the rotation speed increase of a motor. Therefore, by reducing the rear wheel turning assist control gain based on the judgment of the vehicle slip angular velocity and the turning restoration yaw moment, it is possible to reliably suppress the increase in the tire rotation speed generated by the surplus torque exceeding the tire friction circle limit. can do.

  As described above, according to the present embodiment, the turning restoring yaw moment that works to restore the vehicle to the straight traveling state is calculated from the tire rudder angle and the vehicle body slip angle. When the turning restoration yaw moment makes a transition in a direction that promotes turning of the vehicle 1000, the turning assist gain βG is reduced to reduce the turning assist torque. Since the turning recovery yaw moment includes the factors of self-aligning torque and tire lateral force, the road surface condition can be accurately estimated based on the turning recovery yaw moment. Since the torque is reduced, the longitudinal force and lateral force can be optimally controlled within the tire friction circle.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

142 Yaw Rate Sensor 200 Control Device 204 Target Yaw Rate Calculation Unit 206 Vehicle Yaw Rate Calculation Unit 208 Yaw Rate F / B Calculation Unit 222 Vehicle Body Slip Angular Speed Calculation Unit 224 Actual Vehicle Slip Angle Calculation Unit 226 Vehicle Body Behavior Prediction Unit 232 Vehicle Body Additional Moment Calculation Unit 234 Turning Assist Gain calculation unit 236 multiplication unit 1000 vehicle

Claims (7)

A vehicle body additional moment calculator for calculating a vehicle body additional moment to be added to the vehicle body independently of the steering system based on the yaw rate of the vehicle;
A turning restoration yaw moment calculating unit for calculating a turning restoration yaw moment for restoring the turning state of the vehicle to a straight traveling state based on the vehicle body slip angle and the tire rudder angle;
A vehicle slip angular velocity calculating unit for calculating a vehicle slip angular velocity that is a temporal change rate of the vehicle slip angle;
A turn assist control gain calculating unit for calculating a turn assist control gain for correcting the vehicle body additional moment based on the turn restoring yaw moment and the vehicle slip angular velocity;
A correction unit for correcting the vehicle body additional moment based on the turning assist control gain ;
Equipped with a,
The turning assist control gain calculation unit, when the turning restoration yaw moment exceeds a predetermined threshold and increases in a direction opposite to the direction in which the turning state of the vehicle is restored to the straight running state, the turning restoration yaw moment is The vehicle control apparatus , wherein the turning assist control gain is decreased as the value increases, and the predetermined threshold value is decreased as the vehicle body angular velocity increases . The turning restoration yaw moment calculation unit calculates the turning restoration yaw moment based on a map that defines a relationship among the vehicle body slip angle, the tire rudder angle, and the turning restoration yaw moment. Item 2. The vehicle control device according to Item 1 . Said pivoting restoring yaw moment calculating portion, the vehicle body slip angle, in addition to the tire steering angle, based on the longitudinal acceleration of the vehicle, and calculates the turning restoration yaw moment, any of claim 1 or 2 The vehicle control apparatus according to claim 1. Said pivoting restoring yaw moment, the self-aligning torque determined from the vehicle specification value, and wherein the determined and a transverse force of the tire, the control apparatus for a vehicle according to any one of claims 1-3. A target yaw rate calculation unit for calculating a target yaw rate based on the steering angle and the vehicle speed;
A vehicle yaw rate calculation unit for calculating a yaw rate model value from the vehicle model;
A yaw rate sensor that detects the actual yaw rate of the vehicle;
A feedback yaw rate calculation unit that distributes the yaw rate model value and the actual yaw rate based on a difference between the yaw rate model value and the actual yaw rate, and calculates a feedback yaw rate from the yaw rate model value and the actual yaw rate;
With
The vehicle body additional moment calculator is
The vehicle control device according to any one of claims 1 to 4 , wherein the vehicle body additional moment is calculated based on a difference between the target yaw rate and the feedback yaw rate. Characterized in that it comprises a required motor torque calculation unit that calculates a required motor torque for individually controlling the motors driving each of the rear left and right wheels of the vehicle based on the vehicle body additional moment claim 1-5 The vehicle control device according to any one of the above. Calculating a vehicle body additional moment to be applied to the vehicle body independently of the steering system based on the yaw rate of the vehicle;
Calculating a turning restoration yaw moment for restoring the turning state of the vehicle to a straight traveling state based on the vehicle body slip angle and the tire rudder angle;
Calculating a vehicle slip angular velocity that is a temporal change rate of the vehicle slip angle;
Calculating a turning assist control gain for correcting the vehicle body additional moment based on the turning restoring yaw moment and the vehicle slip angular velocity;
Correcting the vehicle body additional moment based on the turning assist control gain ;
Equipped with a,
In the step of calculating the turning assist control gain, when the turning restoration yaw moment exceeds a predetermined threshold value and becomes larger in the direction opposite to the direction in which the turning state of the vehicle is restored to the straight running state, the turning restoration yaw The vehicle control method , wherein the turning assist control gain is decreased as the moment increases, and the predetermined threshold is decreased as the angular velocity of the vehicle slip increases .

Images