JP2017184615A - Vehicle control device and vehicle control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent hunting which is generated in a driving system and perform return to steering assist control corresponding to a high μ path more early, when switching between low μ path control and high μ path control.SOLUTION: A vehicle control device 200 comprises: a vehicle body addition moment calculating portion 232 that calculates a vehicle body addition moment Mg to be added to a vehicle body independently from a handle steering system on the basis of a yaw rate of a vehicle; a slip state determining portion that determines a slip state of the vehicle; and a low μ determination output gain calculating portion 234 that when determining that the vehicle is in the slip state calculates adjustment gain for adjusting the vehicle body addition moment Mg so that the vehicle body addition moment is reduced, and when determining that the vehicle is returned from the slip state, increases the adjustment gain according to degrees of the slip of the vehicle. The slip state is determined based on a difference in rotation speed between left and right wheels and a difference between a feedback yaw rate and a target yaw rate of the vehicle.SELECTED DRAWING: Figure 6

Description

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

  Conventionally, for example, in Patent Document 1 below, a yaw rate sensor value is set as a yaw rate F / B value in an electric vehicle that can independently drive left and right rear wheels and performs running stability control in which a moment around the center of gravity is controlled by a yaw rate. A drive control device is disclosed.

JP-A-10-271613

  When the vehicle is driven using the yaw rate sensor value as the yaw rate F / B value, if the road surface state is switched from high μ to low μ, the tire slips under drive control assuming a high μ road. On the other hand, in drive control assuming a low μ road, sufficient turning performance cannot be obtained on a high μ road. For this reason, it is conceivable to detect the slip condition and switch the drive control of the left and right motors on the high μ road and the low μ road to reduce the motor output while traveling on the low μ road.

  However, if the control of the low μ road is performed by reducing the output of the motor while traveling on the low μ road, and the control returns to the high μ road in the process of returning from the low μ road to the high μ road, the motor The number of revolutions increases rapidly and slips again. In this case, in order to detect the slip state and reduce the output of the motor, control corresponding to the low μ road is performed again. Thereafter, in the process of returning from the low μ road to the high μ road, the above process is repeated, and there is a problem in that hunting is generated by repeatedly increasing and decreasing the rotation speed of the motor.

  On the other hand, in order to prevent hunting of the motor rotation speed as described above, in the process of switching from the low μ road to the high μ road, if it takes longer time to return to the control corresponding to the high μ road in anticipation of safety Since the return to the turning assist control corresponding to the high μ road is delayed, there is a problem that the turning performance is deteriorated.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to reduce the hunting generated in the drive system when switching between low μ road control and high μ road control. An object of the present invention is to provide a new and improved vehicle control device and vehicle control method capable of reliably suppressing and returning to turning assist control corresponding to a high μ road more quickly.

  In order to solve the above-described problem, according to an aspect of the present invention, a vehicle body additional moment calculation unit that calculates a vehicle body additional moment to be added to a vehicle body independently of a steering system based on a yaw rate of the vehicle, and the vehicle A slip state determination unit that determines a slip state of the vehicle, and an adjustment gain that adjusts the vehicle body additional moment so that the vehicle body additional moment is reduced when the vehicle is determined to be in the slip state; An adjustment gain calculation unit that increases the adjustment gain according to the degree of slip of the vehicle when it is determined that the vehicle returns from the slip state, and the slip state determination unit rotates left and right wheels Determining the slip state based on a difference in number and a difference in feedback yaw rate with respect to a target yaw rate of the vehicle, Control device is provided.

  A theoretical vehicle slip angle calculator that calculates a theoretical vehicle slip angle based on a vehicle model; and an actual vehicle slip angle calculator that calculates an actual vehicle slip angle of the vehicle based on a sensor value, the adjustment gain calculator May increase the adjustment gain based on a difference between the theoretical vehicle slip angle and the actual vehicle slip angle.

  The adjustment gain calculation unit may decrease the speed at which the adjustment gain is increased as the difference between the theoretical vehicle slip angle and the actual vehicle slip angle increases.

  The adjustment gain calculation unit determines the previous value of the adjustment gain according to the difference between the theoretical vehicle slip angle and the actual vehicle slip angle every time the adjustment gain is calculated every control cycle. The return gain may be added to increase the adjustment gain.

  A vehicle slip angle ratio calculating unit that calculates a vehicle slip angle ratio by dividing a difference between the theoretical vehicle slip angle and the actual vehicle slip angle by the actual vehicle slip angle; It may be determined according to the angular rate.

  Further, the slip state determination unit is based on a difference between a theoretical difference between the rotational speeds of the left and right wheels calculated from the vehicle model and an actual difference between the rotational speeds of the left and right wheels detected from a sensor. May be used.

  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 the yaw rate of the vehicle;
Determining a slip state of the vehicle; calculating an adjustment gain for adjusting the vehicle body additional moment so that the vehicle body additional moment is reduced when the vehicle is determined to be in the slip state; When the vehicle is determined to return from the slip state, the adjustment gain is increased in accordance with the degree of slip of the vehicle, and in the step of determining the slip state, the left and right wheels are rotated. There is provided a vehicle control method for determining the slip state based on a difference in number and a difference in feedback yaw rate with respect to a target yaw rate of the vehicle.

  As described above, according to the present invention, when switching between low μ road control and high μ road control, hunting generated in the drive system is surely suppressed and turning assist control corresponding to the high μ road is provided. It becomes possible to return to the earlier.

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 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 in which the low micro judgment output gain calculation part computes the low micro judgment output gain micro G. FIG. 13 is a characteristic diagram showing how the low μ determination output gain μG increases in the process of step S266 of FIG. 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.

  Therefore, in this embodiment, the gain of the turn assist control is decreased on a road surface with a low μ. Slip determination is performed when a deviation occurs between the theoretical calculation value and the sensor value for each of the wheel rotation speed and the vehicle body yaw rate during turning assist, and the output gain for turning assist control (low μ determination output gain μG) is reduced. . As a result, the longitudinal force of the rear wheels 104 and 106 decreases, and the lateral force tolerance increases. Therefore, the lateral force of the rear wheels 104 and 106 is not easily saturated, the behavior of the vehicle 1000 can be stabilized, and the occurrence of spin or the like can be avoided.

  On the other hand, in this embodiment, when it is determined that the road surface is changed from low μ to high μ and the difference between the theoretical value and the actual value of the vehicle body yaw rate is reduced, the gain value is restored and the turning assist control is performed. Increase the output gain of to secure the turning force. At this time, if the gain is suddenly increased, it is assumed that the number of rotations of the motor of the rear wheel suddenly increases and the vehicle 1000 again slips. More specifically, when it is determined that the road has returned from the slip state and is a high μ road, the gain is increased in order to switch to the high μ road control, but when the slip occurs again, the gain is decreased again. By repeating this operation, motor speed hunting occurs. In order to prevent hunting, a method of increasing the gain in a slope with time can be considered, but it takes time to return when switching to high μ road control.

  Therefore, in the present embodiment, when the road surface returns from low μ to high μ, the output gain of the turning assist control is gradually increased to suppress the increase in the motor rotation speed that occurs when the control is switched, and the vehicle 1000 is prevented from slipping again. In particular, in the present embodiment, in the process in which the vehicle 1000 returns from the slip state, the gain of the turn assist control is gradually increased according to the degree of slip. The return speed is calculated by calculating the difference between the theoretical calculated value and the actual value of the vehicle slip angle. If the difference in slip angle is small, the degree of slip is small, so the return speed is increased, and if the difference is large, the degree of slip is still large. Reduce the return speed. At this time, a weighting map is used in which the slope of the control return slope is variable according to the degree of slip. As a result, a rapid gain change can be suppressed, hunting of the motor rotation speed and tire rotation speed can be suppressed, and at the same time, the steering assist during turning can be returned early. Compared to increasing the gain with time control, the tire's longitudinal force can be transmitted to the road surface as much as possible, the return to the turn assist control can be performed more quickly, and drivability can be improved. It becomes.

  Therefore, according to the present embodiment, both turning performance stability performance can be achieved on both the low μ road and the high μ road, and hunting of the motor rotation speed can be suppressed at the time of switching the control. Further, it is possible to quickly return the steering assist at the time of turning with respect to the return from the slip state.

  FIG. 5 is a diagram showing the relationship between the longitudinal force and lateral force of the rear wheel. With reference to FIG. 5, the stabilization of the behavior of the vehicle 1000 will be described in detail.

  In the characteristics indicating the relationship between the longitudinal force and the lateral force of the rear wheels 106 and 108 (hereinafter also referred to as tire frictional circle characteristics), for example, the road surface state is high μ and before the gain of the turn assist control is reduced. Since the longitudinal force is generated up to the arrow A51 of the longitudinal axis shown in the left diagram of FIG. 5, 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. 5, 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 the present embodiment, when the road surface becomes low μ, the gain of the turning assist control is decreased. Therefore, as indicated by an arrow A53 in the left diagram of FIG. 5, the longitudinal force is decreased, and the lateral force tolerance is increased. (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 100 is stabilized.

  Thereafter, when the road surface returns to high μ, the tire friction circle returns to C1 in the right diagram of FIG. Therefore, by increasing the gain of the turning assist control, the longitudinal force of the tire can be increased to the solid friction circle C1. At this time, in this embodiment, the gain of the turning assist control is increased according to the degree of slip of the vehicle 1000. Specifically, when the friction circle expands in the order of C2 → C3 → C1, the longitudinal force is increased in the order of arrows A55 → A56 → A57 according to the size of the friction circle. Thereby, since the gain increases as the friction circle of the tire increases, the longitudinal force can be increased in a short time without saturating the longitudinal force.

  On the other hand, when the gain is increased with the passage of time, in order not to saturate the longitudinal force, it is necessary to delay the increase in gain in consideration of a margin. In this case, since the return of the gain is delayed, the turning performance is deteriorated until the gain is returned.

  Therefore, according to the present embodiment, by increasing the gain according to the degree of slip of the vehicle 1000, the longitudinal force can be returned more quickly without saturating the longitudinal force. Therefore, the return to the high μ turning assist control can be performed more quickly, and the turning performance of the vehicle 100 can be greatly improved. Details will be described below.

  FIG. 6 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, 212, 214, 216, 218, and a weighting gain calculation unit 220. , Theoretical vehicle slip angle calculation unit 222, actual vehicle slip angle calculation unit 224, vehicle slip angle ratio calculation unit 226, turning assist control return speed gain calculation unit 228, theoretical left / right difference rotation calculation unit (vehicle model) 230, vehicle body additional moment A calculation unit 232, a low μ determination output gain calculation unit 234, a multiplication unit 236, and a motor required torque calculation unit 238 are configured.

  In FIG. 6, 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. Lateral acceleration sensor 134 detects lateral acceleration Ay 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. 7 is a schematic diagram illustrating a gain map when the weighting gain calculation unit 220 calculates the weighting gain a. As shown in FIG. 7, 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. 7, 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. 7 on the difference γ_diff and calculates a weighting gain a corresponding to the reliability of the vehicle model.

  In FIG. 7, 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).

  Further, when 0.1 <γ_diff or when γ_diff <−0.1, 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. 7 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. Occurs. 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.

  In addition, a gain map area A2 shown in FIG. 7 is an area where the difference γ_diff is large, which corresponds to a wet road surface, a snow road, or a turn with a high G, and the limit of tire slipping. 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. As for the setting of the low μ region A2 shown in FIG. 7, the region where the weighting gain a = 0 may be determined from the design requirements, or the steering stability performance and the riding when the vehicle 1000 actually travels on the low μ road surface. You may decide experimentally from comfort etc.

  In addition, a gain map area A3 shown in FIG. 7 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 considered in consideration of 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. 7 corresponds to a 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. Further, the difference Δγ is input to the low μ determination output gain calculation unit 234.

  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.

  In the control device 200, the deviation between the actual value and the theoretical value of the difference between the left and right rotational speeds of the rear wheels 106 and 108 is within a set threshold value, and the deviation between the target yaw rate γ_tgt and the feedback yaw rate γ_F / B is the threshold. If it is within the value, it is determined that the vehicle 1000 has returned from the slip state, and the output gain for turning assist control is returned. The theoretical vehicle slip angle calculation unit 222, the actual vehicle slip angle calculation unit 224, the vehicle slip angle rate calculation unit 226, the turning assist control return speed gain calculation unit 228, and the low μ determination output gain calculation unit 234 return the output gain. Perform the process.

  The theoretical vehicle slip angle calculation unit 222 calculates the theoretical vehicle slip angle Slip_ang_clc based on the equations (5) and (6) representing the plane two-wheel model. The theoretical vehicle slip angle Slip_ang_clc corresponds to β in the equations (5) and (6). The theoretical vehicle slip angle calculation unit 222 calculates a theoretical vehicle slip angle Slip_ang_clc based on the steering angle θh, the vehicle speed V, and the actual yaw rate γ_sens. The calculated theoretical vehicle slip angle Slip_ang_clc is input to the subtraction unit 214.

The actual vehicle slip angle calculation unit 224 calculates an actual vehicle slip angle Slip_ang_real based on the actual yaw rate γ_sens, the lateral acceleration Ay, and the vehicle speed V. Specifically, the actual vehicle slip angle calculation unit 224 calculates the actual vehicle slip angle Slip_ang_real from the following equation (10). Note that a value detected by the lateral acceleration sensor 134 is used as the lateral acceleration Ay. The calculated actual vehicle slip angle Slip_ang_real is input to the subtracting unit 214.
Slip_ang_real = d (Ay / V-γ_sens) / dt (10)

The subtracting unit 214 calculates a difference ΔSlip_ang between the actual vehicle slip angle Slip_ang_real and the theoretical vehicle slip angle Slip_ang_clc. Specifically, the subtracting unit 214 obtains the difference ΔSlip_ang by subtracting the absolute value of the theoretical vehicle slip angle Slip_ang_clc from the absolute value of the actual vehicle slip angle Slip_ang_real. That is, the difference ΔSlip_ang is calculated from the following equation (11). The calculated difference ΔSlip_ang is input to the vehicle body slip angle rate calculation unit 226.
ΔSlip_ang = | Slip_ang_real | − | Slip_ang_clc |
(11)

The vehicle slip angle ratio calculation unit 226 calculates the vehicle slip angle ratio Slip_ang_rate by dividing the absolute value of the difference ΔSlip_ang by the absolute value of the actual vehicle slip angle Slip_ang_real. That is, the vehicle body slip angle rate Slip_ang_rate is calculated from the following equation (12). The calculated vehicle slip angle rate Slip_ang_rate is input to the turning assist control return speed gain calculation unit 228.
Slip_ang_rate = | ΔSlip_ang | / | Slip_ang_real | (12)

The turn assist control return speed gain calculation unit 228 calculates the turn assist control return speed gain βG based on the vehicle body slip angle rate Slip_ang_rate. The turn assist control return speed gain calculation unit 228 calculates the turn assist control return speed gain βG in order to vary the return speed of the low μ determination output gain μG based on the difference between the theoretical value of the vehicle slip angle and the sensor value. . The turning assist control return speed gain βG is calculated from the following equation (13). The turning assist control return speed gain βG is input to the low μ determination output gain calculation unit 234.
βG = 1−Slip_ang_rate (13)

  On the other hand, the control device 200 compares the actual value of the difference between the left and right rotational speeds of the rear wheels 104 and 106 with the theoretical value, the actual value deviates from the theoretical value, and the difference between the target yaw rate γ_tgt and the feedback yaw rate γ_F / B When it occurs, it is determined that the vehicle is slipping, and the assist torque of the rear wheels 104 and 106 is reduced. Therefore, the theoretical left / right difference rotation calculation unit 230 calculates the left / right difference rotation theoretical value ΔNew_clc based on the vehicle speed V and the steering angle θh. The left-right differential rotation theoretical value ΔNew_clc is the rotational speed difference between the left and right rear wheels 104 and 106 that is geometrically determined according to the radius of rotation. Further, the subtracting unit 216 calculates a left-right difference rotation actual value ΔNew_real which is a difference between the rotation speed of the left rear wheel 104 and the rotation speed of the right rear wheel 106. Note that the left-right difference rotation actual value ΔNew_real can be obtained from the difference in rotation speed between the left and right wheel speed sensors 127, 128. Note that the left-right differential rotation actual value ΔNew_real may be obtained from the differential rotation of the left and right front wheels 100, 102.

The left / right differential rotation theoretical value ΔNew_clc and the left / right differential rotation actual value ΔNew_real are input to the subtracting unit 218. The subtracting unit 218 calculates ΔNew by subtracting the right / left difference rotation actual value ΔNew_real from the left / right difference rotation theoretical value ΔNew_clc. That is, ΔNew is calculated from the following equation (14). ΔNew is input to the low μ determination output gain calculation unit 234.
ΔNew = ΔNew_clc−ΔNew_real (14)

  The low μ determination output gain calculation unit 234 determines the slip determination flag μjud and calculates the low μ determination output gain μG based on the differences ΔNew and Δγ. Specifically, the low μ determination output gain calculation unit 234 determines the slip determination flag μjud of the vehicle 1000 by comparing the difference ΔNew with a threshold and comparing the difference Δγ with a threshold. Details will be described later with reference to the flowchart shown in FIG. When determining slip using only the difference ΔNew, for example, when the vehicle 1000 gets over a step or the like, the difference ΔNew temporarily exceeds the threshold value, although it is not in a slip state. There is a possibility of erroneous determination as a slip state. If slip determination is performed based only on the difference Δγ, there is a possibility that the slip state determination is delayed due to a response delay of Δγ. By performing the slip determination using both the difference ΔNew and the difference Δγ, the slip state can be determined with high accuracy. In the present embodiment, the “slip state determination unit” that determines the slip state of the vehicle 1000 includes a theoretical left / right difference rotation calculation unit 230, a subtraction unit 218, and a low μ determination output gain calculation unit 234.

  Further, the low μ determination output gain calculation unit 234 calculates a low μ determination output gain μG based on the differences ΔNew and Δγ and the slip determination flag μjud. Here, the maximum value of the low μ determination output gain μG used for the control is 1, and if the road surface state is high μ (μjud = 0), the value of the low μ determination output gain μG is set to 1. .

  On the other hand, when it is determined that the vehicle 1000 tends to slip (μjud = 1), the low μ determination output gain calculation unit 234 sets the value of the low μ determination output gain μG so that the vehicle body additional moment is reduced. Reduce. In this embodiment, as an example, when it is determined that the vehicle 1000 tends to slip (μjud = 1), the value of the low μ determination output gain μG is reduced to 0.1.

Thereafter, when the road surface state transitions from low μ to high μ and the tendency of the vehicle 1000 to slip becomes small, the low μ determination output gain calculation unit 234 increases the low μ determination output gain so that the reduced vehicle body additional moment increases. Change μG. At this time, the low μ determination output gain calculation unit 234 changes the low μ determination output gain μG according to the degree of slip of the vehicle 1000 so that the low μ determination output gain μG approaches 1 as the tendency to slip is smaller. Control. Specifically, the low μ determination output gain calculation unit 234 adds the turning assist control return speed gain βG to the previous value μG ′ of the low μ determination output gain μG based on the following equation (15). The μ judgment output gain μG is calculated.
μG = μG ′ + βG (15)

  In equation (15), the turning assist control return speed gain βG is a value obtained from the vehicle body slip angle rate Slip_ang_rate. The vehicle slip angle rate Slip_ang_rate is calculated from the difference ΔSlip_ang between the actual vehicle slip angle Slip_ang_real and the theoretical vehicle slip angle Slip_ang_clc, and the value of ΔSlip_ang becomes smaller as the tendency of the vehicle 1000 to slip becomes smaller. That is, when the road surface is high μ and the tendency of the vehicle 1000 to slip is small, the value of the actual vehicle slip angle Slip_ang_real obtained from the sensor value is close to the theoretical vehicle slip angle Slip_ang_clc obtained by calculation. On the other hand, when the road surface is low μ and the vehicle 1000 tends to slip, the actual vehicle slip angle Slip_ang_real obtained from the sensor value deviates from the theoretical vehicle slip angle Slip_ang_clc obtained by calculation. Therefore, based on the equation (13), the smaller the tendency of the vehicle 1000 to slip, the larger the value of the turn assist control return speed gain βG, and as a result, the value of the low μ determination output gain μG increases. The return of the low μ judgment output gain μG is variable by the difference ΔSlip_ang between the theoretical value and the actual value of the vehicle slip angle. Thereby, the smaller the tendency to slip, the faster the speed at which the low μ determination output gain μG is returned to 1.

  The low μ determination output gain μG calculated by the low μ determination output 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 low μ determination output gain μG to calculate a correction value Mg ′ for the vehicle body additional moment Mg. As an example, when it is determined that the vehicle 1000 has a tendency to slip (μjud = 1) and the low μ determination output gain calculation unit 234 determines that the low μ state, the value of the low μ determination output gain μG is 0. Therefore, the vehicle body additional moment Mg is corrected to a value of 1/10.

  The correction value Mg ′ is input to the motor required torque calculation unit 238. The motor required torque calculation unit 238 converts the moment into torque using the correction value Mg ′, and calculates ΔTv from the following equation (16). Then, the motor required torque calculation unit 238 calculates the additional torque Tvmot from the following equation (17).

  In equation (16), 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 (16). Then, the motor torque of each of the rear wheels 104 and 106 necessary for generating the correction value Mg ′ is obtained by Expression (17).

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 command value reqTq is calculated from the following equation (18).
reqTq = reqF * TireR * Gratio (18)
In Expression (18), 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 is turning, an additional torque Tvmot based on the vehicle body additional moment Mg ′ calculated from the equation (17) 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 (19) to (22). The motor required torque calculation unit 238 calculates motor torque instruction values TqmotFl, TqmotFr, TqmotRl, and TqmotRr for each of the motors 108, 110, 112, and 114 based on the equations (19) to (22).
TqmotFl (motor torque instruction value of the left front wheel) = reqTq / 4 (19)
TqmotFr (right front wheel motor torque instruction value) = reqTq / 4 (20)
TqmotRl (Left rear wheel motor torque instruction value)
= ReqTq / 4- (± Tvmot) (21)
TqmotRr (Right rear wheel motor torque instruction value)
= ReqTq / 4 + (± Tvmot) (22)
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. 8 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 yaw rate γ_Tgt is performed based on the additional torque Tvmot. For this reason, in the next step S124, motor torque instruction values of the motors 108, 110, 112, 114 are calculated from the equations (19) to (22) 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 acceleration of the vehicle 1000 is detected by the longitudinal acceleration sensor 132 and the lateral acceleration sensor 134. After step S126, the process returns to step S114.

  Next, main processing of the processing of FIG. 8 will be described in detail. FIG. 9 is a flowchart showing the process of step S122 of FIG. Here, FIG. 9 is a flowchart illustrating a process in which the weighting gain calculation unit 220 calculates the weighting gain a. The process of FIG. 9 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 to calculate the difference Δγ in step S224 in FIG.

  FIG. 10 is a flowchart illustrating processing 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 to calculate the feedback yaw rate γ_F / B in step S204 of FIG.

  FIG. 11 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 low μ determination output gain calculation unit 234 calculates the low μ determination output gain μG. In the next step S230, ΔTv is calculated based on the equation (16), and the additional torque Tvmot is calculated based on the equation (17). Based on the calculated additional torque Tvmot, a motor torque instruction value for each wheel is calculated in step S124 of FIG.

  FIG. 12 is a flowchart illustrating a process in which the low μ determination output gain calculation unit 234 calculates the low μ determination output gain μG. First, in step S240, the differences Δγ and ΔNew are input to the low μ determination output gain calculation unit 234. Further, the lateral acceleration Ay and the actual yaw rate γ are input to the theoretical vehicle slip angle calculation unit 222. In the next step S242, the state of the slip determination flag μjud is determined, and it is determined whether μjud = 0. When μjud = 0, the road surface state is high μ and there is no tendency to slip, so the process proceeds to step S244. In step S244, it is determined whether or not ΔNew ≦ 150 [rpm]. If ΔNew ≦ 150 [rpm], the process proceeds to step S246. In step S246, the turning assist gain μG is set to 1 (μG = 1). As described above, when the slip determination flag μjud is set to 0 in the previous cycle, the road surface state is high μ and there is no tendency to slip on the condition that ΔNew is 150 [rpm] or less. And turning assist gain μG is set to 1. As a result, the correction value Mg ′ coincides with the vehicle body additional moment Mg calculated by the vehicle body additional moment calculation unit 232, and the motor torque instruction values TqmotFl, TqmotFr of the motors 108, 110, 112, 114 are based on the vehicle body additional moment Mg. TqmotRl and TqmotRr are calculated.

  If ΔNew> 150 [rpm] in step S244, the process proceeds to step S248 to determine whether or not | Δγ | ≦ 0.75 [rad / s]. If | Δγ | ≦ 0.75 [rad / s], the process proceeds to step S246. Thus, even when ΔNew exceeds 150 [rpm], if | Δγ | ≦ 0.75 [rad / s], the road surface state is high μ and there is no tendency to slip. to decide. Thereby, for example, when ΔNnew temporarily exceeds 150 [rpm] when traveling on a step or the like, the slip determination (μjud = 1) can be avoided.

  If μjud = 1 in step S242, the process proceeds to step S250. In step S250, it is determined whether or not | Δγ | <0.075 [rad / s]. If | Δγ | <0.075 [rad / s], the process proceeds to step S252. In this case, since the absolute value of Δγ is sufficiently small, it is assumed that the road surface has transitioned from low μ to high μ, and the low μ determination output gain μG is restored to 1 in the processing after step S252. Process.

  In step S252, the actual vehicle slip angle Slip_ang_real is calculated using equation (10). In the next step S254, the difference ΔSlip_ang is calculated from the equation (11).

  In the next step S256, the vehicle body slip angle rate Slip_ang_rate is calculated from the equation (12). In the next step S258, the turning assist control return speed gain βG is calculated from the equation (13).

  Note that the vehicle slip angle rate Slip_ang_rate is a value obtained by dividing the difference ΔSlip_ang by the actual vehicle slip angle Slip_ang_real. When the vehicle 1000 is in the slip state, Slip_ang_real> Slip_ang_clc, so the vehicle slip angle rate Srip_ang_rate. A value of 1 or less. Therefore, the value of the turning assist control return speed gain βG calculated in step S258 can be set to a value between 0 and 1. If the degree of slip of the vehicle 1000 is large, the turning assist control return speed gain βG is close to 0, and if the degree of slip of the vehicle 1000 is small, the turning assist control return speed gain βG is close to 1. Thereby, the return speed of the low μ determination output gain μG can be varied according to the degree of slip of the vehicle 1000.

  In the next step S260, it is determined whether or not the value of the low μ determination output gain μG is 1 or more. If μG ≧ 1, the process proceeds to step S262. In step S262, the slip determination flag is set to 0. In the next step S264, the value of the low μ determination output gain μG is set to 1 (μG = 1).

  If μG <1 in step S260, the process proceeds to step S266. In step S266, the low μ determination output gain μG is calculated by the equation (15). If slip occurs while the low μ judgment output gain μG is increasing in step S266, the low slip judgment flag μjud is set to 1 in step S268, and the value of the low μ judgment output gain μG is set to 0.1 in step S270. Will be reset.

  If | Δγ | ≧ 0.075 [rad / s] in step S250, the process proceeds to step S268. In this case, since the absolute value of Δγ is 0.075 [rad / s] or more, it is determined that the vehicle 1000 is still in the slip state, and the slip determination flag is set to 1 in step S268 (μjud = 1). Similarly, if | Δγ |> 0.75 [rad / s] in step S248, the process proceeds to step S268. In this case, since ΔNew is larger than 150 [rpm] and | Δγ |> 0.75 [rad / s], ΔNew does not temporarily exceed 150 [rpm] due to a step or the like. Then, it is determined that the vehicle 1000 is in the slip state, and the slip determination flag is set to 1 in step S268 (μjud = 1).

  After step S268, the process proceeds to step S270. In step S270, the low μ determination output gain μG is set to 0.1 (μG = 0.1). Thereby, when the vehicle 1000 is in a slip state, the vehicle body additional moment Mg is corrected to a value of 1/10. As a result, the longitudinal force of the rear wheels 104 and 106 decreases, and the lateral force tolerance increases. Accordingly, the behavior of the vehicle 1000 is stabilized without oversteering.

  FIG. 13 is a characteristic diagram showing how the low μ determination output gain μG increases in the process of step S266 of FIG. As described above, as the vehicle body slip angle rate Slip_ang_rate decreases, the value of the turning assist control return speed gain βG increases, and the amount of increase in the low μ determination output gain μG in step S266 increases. The smaller the value of the difference ΔSlip_ang, the smaller the value of the vehicle body slip angle rate Slip_ang_rate. Therefore, as shown in FIG. 13, in step S266, the smaller the value of the difference ΔSlip_ang, the larger the increase rate of the low μ determination output gain μG, and the low μ determination output gain μG is returned to “1” earlier. Can do.

  As described above, the slip state of the vehicle 1000 can be determined based on the value of the difference ΔSlip_ang, and the smaller the value of the difference ΔSlip_ang, the closer the values of the actual vehicle slip angle Slip_ang_real and the theoretical vehicle slip angle Slip_ang_clc. It can be determined that the vehicle 1000 is not in the slip state. On the other hand, as the value of the difference ΔSlip_ang increases, the value of the actual vehicle slip angle Slip_ang_real and the theoretical vehicle slip angle Slip_ang_clc deviate, and it can be determined that the vehicle 1000 is in a slip state. Therefore, by increasing the increase rate of the low μ determination output gain μG as the value of the difference ΔSlip_ang is smaller, the increase rate of the low μ determination output gain μG increases as the degree of slip of the vehicle 1000 decreases. The μ judgment output gain μG can be returned to “1” earlier. In addition, as the value of the difference ΔSlip_ang is larger, the increase rate of the low μ determination output gain μG is decreased, so that the increase rate of the low μ determination output gain μG is smaller and lower as the slip of the vehicle 1000 is larger. It is possible to reliably prevent the vehicle 1000 from slipping again in the process of returning the μ determination output gain μG to “1”. As described above, when the condition for returning the low μ judgment output gain μG is satisfied, the slope of the slope is varied depending on the difference between the theoretical value of the vehicle slip angle and the sensor value, and the motor speed is rapidly changed. Can be prevented from occurring continuously, and at the same time, the return to the turning assist control can be accelerated. Therefore, it is possible to prevent the hunting of the motor rotation speed when the control is switched from the low μ to the high μ and to improve the turning performance by speeding up the return to the turning assist control.

  FIG. 14 and FIG. 15 are characteristic diagrams for explaining the effects when the control according to the present embodiment is performed. Here, FIG. 14 shows a case where the control according to the present embodiment (gain reduction at low μ and return of gain when switching from low μ to high μ) is not performed. On the other hand, FIG. 15 shows a case where the control according to the present embodiment is performed. FIGS. 14 and 15 both simulate the case where slalom running is performed on snow. 14 and 15, the upper diagram shows the left front wheel rotation speed, the right front wheel rotation speed, the left rear wheel rotation speed, and the right rear wheel rotation speed, respectively. 14 and 15, the middle diagram shows the steering angle θh, the target yaw rate γ_Tgt, and the actual yaw rate γ_sens. 14 and 15, the lower diagrams show the left front wheel motor torque instruction value, the right front wheel motor torque instruction value, the left rear wheel motor torque instruction value, the right rear wheel motor torque instruction value, and the vehicle speed, respectively. ing. In each of FIGS. 14 and 15, the time on the horizontal axis corresponds.

  As shown in the upper diagram of FIG. 14, when the control according to the present embodiment is not performed, the value of the low μ determination output gain μG is maintained at 1, so that the left rear wheel rotational speed and the right after time t1. The rear wheel speed is greatly hunting in opposite directions. Further, as shown in the lower diagram of FIG. 14, the torque variation between the left rear wheel motor torque instruction value and the right rear wheel motor torque instruction value is large.

  On the other hand, as shown in the upper diagram of FIG. 15, when the control according to the present embodiment is performed, if the difference between the left rear wheel rotational speed and the right rear wheel rotational speed becomes large at time t11, the low μ judgment output Since the value of the gain μG decreases (μG = 0.1) and the subsequent vehicle body additional moment decreases, it can be seen that hunting of the left rear wheel rotation speed and the right rear wheel rotation speed is suppressed. Further, as shown in the lower diagram of FIG. 15, the left rear wheel motor torque instruction value and the right rear wheel motor torque instruction value are suppressed from fluctuations in torque compared to FIG.

  As described above, when the control according to the present embodiment is performed, even if it is determined that the low μ determination output gain μG is decreased and then the low μ is switched to the high μ, it is determined according to the degree of slip. Thus, since the value of the low μ determination output gain μG returns to 1, it is possible to reliably suppress hunting of the motor rotation speed and the torque instruction value.

  Further, as shown in the middle diagram of FIG. 14, when the control according to the present embodiment is not performed, the steering angle θh, the target yaw rate γ_Tgt, and the actual yaw rate greatly deviate, and the steering angle θh and the actual yaw rate γ_sens. There is a case where the driver deviates and the driver performs reverse steer. For this reason, a complicated operation of the steering is required.

  On the other hand, as shown in the middle diagram of FIG. 15, when the control according to the present embodiment is performed, the steering steering angle θh temporarily differs from the target yaw rate γ_Tgt and the actual yaw rate in the vicinity of time t11. However, after that, the steering angle θh follows the target yaw rate γ_Tgt and the actual yaw rate. Therefore, the driver can perform stable steering.

  As described above, according to this embodiment, when it is determined that the vehicle 1000 is in the slip state, the lateral force of the tire can be increased by reducing the value of the low μ determination output gain μG. Thus, it is possible to reliably prevent the vehicle 1000 from slipping. Further, when the vehicle 1000 is expected to recover from the slip state, the value of the low μ determination output gain μG is gradually restored according to the degree of slip when the degree of slip is large, and the degree of slip is small In this case, the value of the low μ judgment output gain μG is returned earlier. As a result, it is possible to reliably prevent hunting from occurring in the rotational speed of the motor due to a rapid change in the low μ determination output gain μG, and it is possible to quickly recover the longitudinal force when the degree of slip is small. Therefore, it is possible to improve the turning performance.

  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 Theoretical Vehicle Slip Angle Calculation Unit 224 Actual Vehicle Slip Angle Calculation Unit 226 Vehicle Body Slip Angle Ratio Calculation Unit 230 Theoretical Left / Right Difference Rotation Calculation Unit 232 body added moment calculation unit 234 low μ determination output gain calculation unit 1000 vehicle

Claims (9)

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 slip state determination unit for determining a slip state of the vehicle;
When it is determined that the vehicle is in the slip state, an adjustment gain for adjusting the vehicle body additional moment is calculated so that the vehicle body additional moment is reduced, and it is determined that the vehicle returns from the slip state. An adjustment gain calculation unit that increases the adjustment gain according to the degree of slip of the vehicle,
With
The control apparatus for a vehicle, wherein the slip state determination unit determines the slip state based on a difference in rotation speed between left and right wheels and a difference in feedback yaw rate with respect to a target yaw rate of the vehicle. A theoretical vehicle slip angle calculation unit for calculating a theoretical vehicle slip angle based on a vehicle model;
An actual vehicle slip angle calculating unit that calculates an actual vehicle slip angle of the vehicle body based on the sensor value;
With
2. The vehicle control device according to claim 1, wherein the adjustment gain calculation unit increases the adjustment gain based on a difference between the theoretical vehicle slip angle and the actual vehicle slip angle.   3. The vehicle control according to claim 2, wherein the adjustment gain calculation unit decreases a speed at which the adjustment gain is increased as a difference between the theoretical vehicle slip angle and the actual vehicle slip angle increases. apparatus.   The adjustment gain calculation unit returns the value determined in accordance with the difference between the theoretical vehicle slip angle and the actual vehicle slip angle to the previous value of the adjustment gain every time the adjustment gain is calculated every control cycle. The vehicle control device according to claim 3, wherein the adjustment gain is increased by adding a gain. A vehicle slip angle ratio calculating unit for calculating a vehicle slip angle ratio by dividing a difference between the theoretical vehicle slip angle and the actual vehicle slip angle by the actual vehicle slip angle;
The vehicle control device according to claim 4, wherein the return gain is determined according to the vehicle body slip angle rate.   The slip state determination unit determines the slip state based on a difference between a theoretical difference between left and right wheel rotation speeds calculated from a vehicle model and an actual difference between left and right wheel rotation speeds detected from a sensor. The vehicle control device according to claim 1, wherein: 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 claim 1, wherein the vehicle body additional moment is calculated based on a difference between the target yaw rate and the feedback yaw rate.   The motor request torque calculation part which calculates the motor request torque for controlling separately the motor which drives each of the back right-and-left wheel of the said vehicle based on the said vehicle body additional moment is characterized by the above-mentioned. 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;
Determining a slip state of the vehicle;
Calculating an adjustment gain for adjusting the vehicle body additional moment so that the vehicle body additional moment is reduced when it is determined that the vehicle is in the slip state;
Increasing the adjustment gain according to the degree of slip of the vehicle when it is determined that the vehicle returns from the slip state;
With
In the step of determining the slip state, the slip state is determined based on a difference in rotation speed between left and right wheels and a difference in feedback yaw rate with respect to a target yaw rate of the vehicle.

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