JP7635589B2 - Driving force control method and driving force control device - Google Patents

Description

The present invention relates to a driving force control method and a driving force control device.

Patent Document 1 proposes a vehicle occupant posture control device that predicts changes in vehicle acceleration and changes the support state of the vehicle seat for the occupant to stabilize the occupant's posture and suppress car sickness in the occupant. In particular, this vehicle occupant posture control device operates movable parts of the vehicle seat (seat back support parts, armrests, etc.) to support the occupant's body in accordance with the acceleration before the acceleration occurs due to steering of the vehicle, such as when changing lanes.

JP 2007-71370 A

However, the device in Patent Document 1 requires the use of a mechanical structure to allow the vehicle seat to move, which raises concerns about the complexity of the vehicle structure and increased manufacturing costs.

The object of the present invention is therefore to provide a driving force control method and driving force control device that can suppress car sickness in occupants caused by changes in vehicle acceleration with a simpler configuration.

According to one aspect of the present invention, there is provided a driving force control method for controlling a driving force distribution to each of a first driving source connected to a front wheel and a second driving source connected to a rear wheel so that the pitch angle of the vehicle behaves as desired. In this driving force control method, a pitch rate adjustment process is executed to adjust a pitch rate based on a required acceleration for the vehicle so as to generate a pitch displacement in a direction that cancels the longitudinal acceleration corresponding to the required acceleration. The pitch rate adjustment process adjusts the pitch rate by controlling the driving force distribution so that the driving force of the first driving source and the driving force of the second driving source are mutually different in positive and negative . The pitch rate adjustment process is also executed after a command to change the required acceleration is issued and before the timing when the longitudinal acceleration actually changes.

The present invention makes it possible to suppress car sickness in occupants caused by changes in vehicle acceleration with a simpler configuration.

FIG. 1 is a diagram illustrating the configuration of a vehicle in which a driving force control method according to an embodiment of the present invention is executed. FIG. 2 is a block diagram illustrating the functional configuration of the driving force control device that executes the driving force control method. FIG. 3 is a diagram for explaining the pitch motion of a vehicle. FIG. 4 is a flowchart illustrating the driving force control method. FIG. 5 is a map illustrating the operating points of the vehicle when the first corrective pitch rate is set. FIG. 6 is a time chart showing the control results when the pitch rate adjustment process is executed when the vehicle is accelerating. FIG. 7 is a time chart showing the control results when the pitch rate adjustment process is executed when the vehicle is decelerating. FIG. 8 is a time chart showing an example of a control result when the second corrected pitch rate is applied.

Each embodiment of the present invention will be described in detail below with reference to the drawings.

Figure 1 is a diagram illustrating the configuration of a vehicle 100 in which the driving force control method of this embodiment is executed.

In addition, the vehicle 100 of this embodiment is assumed to be an electric vehicle or a hybrid vehicle that has a drive motor 10 as a drive source and can run using the driving force of the drive motor 10.

The drive motor 10 is composed of a front wheel motor 10f serving as a first electric motor provided at a position in front of the vehicle 100 (hereinafter referred to as the "front wheel side") and driving the front wheels 11f, and a rear wheel motor 10r serving as a second electric motor provided at a position in the rear of the vehicle (hereinafter referred to as the "rear wheel side") and driving the rear wheels 11r.

The front wheel motor 10f is configured as a three-phase AC motor. The front wheel motor 10f generates a driving force by receiving power from a battery as a power source. The driving force generated by the front wheel motor 10f is transmitted to the front wheels 11f via a front wheel transmission 16f and a front wheel drive shaft 21f. The front wheel motor 10f also converts regenerative driving force generated when the front wheel motor 10f rotates along with the front wheels 11f during the running of the vehicle 100 into AC power. The power supplied to the front wheel motor 10f is adjusted by a front wheel inverter 12f. In particular, the front wheel inverter 12f drives the front wheel motor 10f with a driving force based on the total driving force required for the vehicle 100 (hereinafter also referred to as "total required driving force _Ffr ") and the distribution ratio κ determined for the front wheel motor 10f (hereinafter also referred to as "front wheel driving force _Ff ").

On the other hand, the rear wheel motor 10r is configured as a three-phase AC motor. The rear wheel motor 10r generates a driving force by receiving a supply of electric power from a battery as a power source. The driving force generated by the rear wheel motor 10r is transmitted to the rear wheel 11r via a rear wheel transmission 16r and a rear wheel drive shaft 21r. The rear wheel motor 10r also converts a regenerative driving force generated when the rear wheel motor 10r rotates along with the rear wheel 11r during the running of the vehicle 100 into AC power. The electric power supplied to the rear wheel motor 10r is adjusted by a rear wheel inverter 12r. In particular, the rear wheel inverter 12r drives the rear wheel motor 10r with a driving force (hereinafter also referred to as "rear wheel driving force _Fr ") based on the total required driving force _Ffr and an allocation ratio κ determined for the rear wheel motor 10r.

Furthermore, the vehicle 100 is provided with a controller 50 as a driving force control device that controls the driving force distribution (that is, the front wheel driving force _Ff and the rear wheel driving force _Fr ) of the vehicle 100 based on various input information.

The controller 50 is composed of a computer equipped with a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input/output interface (I/O interface), and is programmed to execute each process in the vehicle control described below. In particular, the functions of the controller 50 can be realized by any on-board computer such as a vehicle controller (VCM: Vehicle Control Module), a vehicle motion control device (VMC: Vehicle Motion Controller), and a motor controller, and/or a computer installed outside the vehicle 100. The controller 50 may be realized by a single piece of computer hardware, or may be realized by distributing various processes across multiple computer hardware.

Furthermore, the various input information (estimated values or detected values) input to the controller 50 includes the amount of operation of the accelerator pedal mounted on the vehicle 100 (hereinafter also referred to as "accelerator pedal opening APO"), the pitch angle θ, and the acceleration in the longitudinal direction of the vehicle 100 (hereinafter also referred to as "longitudinal acceleration a"). In addition, the input information may include, as necessary, a detected value of the steering angle of the vehicle 100, a detected value of the road surface gradient (gradient angle) on the road on which the vehicle 100 is traveling, and/or a detected value of friction (road surface μ) on the road on which the vehicle 100 is traveling.

In this embodiment, the accelerator opening APO is a parameter that represents the value of the longitudinal acceleration a required for the vehicle 100. On the other hand, when the vehicle 100 is equipped with a so-called automatic driving function and at least the required acceleration a _fr is determined by a predetermined automatic driving controller (such as an ADAS "Advanced Driver Assistance Systems" controller or an AD "Autonomous Driving" controller), the value of the longitudinal acceleration a required is determined based on the command driving force. Therefore, hereinafter, this will be collectively referred to as "required acceleration a _fr ".

The functions of the controller 50 are explained in more detail below.

Figure 2 is a block diagram explaining the configuration of the controller 50. As shown in the figure, the controller 50 has a total required driving force calculation unit 52, a basic driving force distribution unit 53, a required jerk calculation unit 55, and a pitch rate adjustment unit 56.

The total required driving force calculation unit 52 receives the accelerator opening APO and other parameters such as vehicle speed as input, and calculates a total required driving force _Ffr , which is the sum of driving forces required for the vehicle 100. For example, the total required driving force calculation unit 52 can read out from an arbitrary memory a predetermined map that defines an appropriate total required driving force _Ffr corresponding to the accelerator opening APO and vehicle speed, and calculate the total required driving force _Ffr by applying the input accelerator opening APO and vehicle speed to the map. The total required driving force calculation unit 52 then outputs the calculated total required driving force _Ffr to the basic driving force allocation unit 53.

The basic driving force distribution unit 53 receives the total required driving force _Ffr from the total required driving force calculation unit 52 as an input, and calculates a basic value _of the front wheel driving force _Ff (hereinafter also referred to as "basic front wheel driving force _{Ff_b} ") and a basic value of the rear wheel driving force _Fr (hereinafter also referred to as "basic rear wheel driving force _{Fr_b} ") from a predetermined basic distribution ratio κb. Here, the basic distribution ratio _κb is a basic value of the distribution ratio κ determined by an experiment, a simulation, or the like so that the vehicle characteristics of the vehicle 100 have desired characteristics. Note that the term vehicle characteristics used in this embodiment mainly includes characteristics related to the efficiency of energy consumed in the operation of the vehicle 100, such as running (fuel consumption performance or power consumption performance), characteristics related to the difficulty of slipping at the front wheels 11f or the rear wheels 11r (slip performance), and the ability of the longitudinal acceleration a to follow the required acceleration _afr (power performance).

In addition, the specific value of the basic distribution ratio κ _b may be appropriately changed depending on the specifications and driving scene of the vehicle 100. As an example, when traveling straight on a flat paved road at a constant speed, the basic distribution ratio κ _b can be set to 50 (front wheels): 50 (rear wheels) so that the front wheel drive force F _f and the rear wheel drive force F _r are the same value from the viewpoint of realizing preferable vehicle characteristics. Note that, based on the basic distribution ratio κ _b determined from the viewpoint of realizing the vehicle characteristics, the basic value of the pitch angle θ of the vehicle 100 (hereinafter also referred to as "basic pitch angle θ _{_b} ^* ") and the basic value of the pitch rate ω (hereinafter also referred to as "basic pitch rate ω _{_b} ^* ") are determined. The meanings of the pitch angle θ and the pitch rate ω in this embodiment will be described.

FIG. 3 is a diagram showing a pitch motion of the vehicle 100. As shown in the figure, the pitch angle θ in this embodiment is defined as a displacement in the pitch direction (the direction of rotation around an axis passing through the center of gravity G and extending in the vehicle width direction) relative to the horizontal direction around the center of gravity G of the vehicle 100. In particular, in this embodiment, the sign of the pitch angle θ is set so that the direction in which the front wheels 11f of the vehicle 100 are lifted (nose-up direction) is positive, and the direction in which the rear wheels 11r are lifted (nose-down direction) is negative. Furthermore, the pitch rate ω is defined as the time rate of change of this pitch angle θ (i.e., the pitch angular velocity). The pitch angle θ and the pitch rate ω change depending on the above-mentioned distribution ratio κ of the driving force and various driving environments (such as road surface unevenness and road surface gradient). In other words, the pitch angle θ and the pitch rate ω can be controlled by manipulating the magnitudes (driving force distribution) of the front wheel driving force F _f and the rear wheel driving force F _r, respectively.

Returning to FIG. 2 , the basic driving force distribution unit 53 outputs the calculated basic front wheel driving force F _{f_b} and basic rear wheel driving force F _{r_b} to the pitch rate adjustment unit 56 .

The pitch rate adjustment unit 56 receives the required acceleration _afr , the basic front wheel drive force _{Ff_b} , and the basic rear wheel drive force _{Fr_b} as input information. Then, based on the required acceleration _afr , the pitch rate adjustment unit 56 determines the corrected front wheel drive force _{Ff_c} and the corrected rear wheel drive force _{Fr_c} to be set under predetermined conditions when accelerating or decelerating the vehicle 100. In particular, the pitch rate adjustment unit 56 executes a pitch rate adjustment process described later that determines the corrected pitch rate _{ω_c} ^* .

Then, the pitch rate adjustment unit 56 determines the front wheel driving force _Ff and the rear wheel driving force _Fr when the pitch rate ω is made to coincide with the corrected pitch rate ω _{_c} ^* obtained in the pitch rate adjustment process as the corrected front wheel driving force F _{f _c} and the corrected rear wheel driving force F _{r _c} , respectively.

More specifically, the pitch rate adjustment unit 56 calculates a corrected front wheel drive force F _{f_c} and a corrected rear wheel drive force F _{r_c} for bringing the pitch rate ω closer to the corrected pitch rate ω _{_c} ^* when accelerating or decelerating the vehicle 100. More specifically, when the pitch angle θ is decreased (when the vehicle 100 is nose-down), the pitch rate adjustment unit 56 calculates the corrected front wheel drive force F _{f_c} and the corrected rear wheel drive force F _{r_c} so that the corrected pitch rate ω _{_c} ^* becomes a negative value. Also, when the pitch angle θ is increased (when the vehicle 100 is nose-up), the pitch rate adjustment unit 56 calculates the corrected front wheel drive force F _{f_c} and the corrected rear wheel drive force F _{r_c} so that the corrected pitch rate ω _{_c} ^* becomes a positive value.

In particular, the pitch rate adjustment unit 56 determines the corrected pitch rate _{ω_c} ^* by referring to information on the anti-dive angle φ of the front suspension, which is determined by the structure of the vehicle 100, from a predetermined storage area. Note that the information on the anti-dive angle φ is input to the above storage area at an initial stage, such as at the time of shipment from the factory.

More specifically, when the antidive angle φ of the vehicle 100 is positive, the pitch rate adjuster 56 sets the corrected front wheel drive force F _{f_c} in an increasing direction and/or the corrected rear wheel drive force F _{r_c} in a decreasing direction to set the corrected pitch rate ω _{_c} ^* to a negative value (nose down). Also, when the antidive angle φ is positive, the pitch rate adjuster 56 sets the corrected front wheel drive force F _{f_c} in a decreasing direction and/or the corrected rear wheel drive force F _{r_c} in an increasing direction to set the corrected pitch rate ω _{_c} ^* to a positive value (nose up). In particular, when the antidive angle φ is positive and the vehicle 100 is in an accelerating state (required acceleration a _fr > 0), the pitch rate adjuster 56 of this embodiment sets the corrected pitch rate ω _{_c} ^* to reduce the pitch angle θ by setting the rear wheel drive force F _r to a negative value. Furthermore, in the present embodiment, when the anti-dive angle φ is positive and the vehicle 100 is in a decelerating state (required acceleration a _fr < 0), the pitch rate adjustment unit 56 determines the corrected pitch rate ω _{_c} ^* so as to increase the pitch angle θ by setting the front wheel drive force F _f to a negative value.

On the other hand, when the antidive angle φ of the vehicle 100 is negative, the pitch rate adjuster 56 sets the corrected front wheel drive force F _{f_c} in a decreasing direction and/or the corrected rear wheel drive force F _{r_c} in an increasing direction to make the corrected pitch rate ω _{_c} ^* a negative value (nose down). Also, when the antidive angle φ is negative, the pitch rate adjuster 56 sets the corrected front wheel drive force F _{f_c} in an increasing direction and/or the corrected rear wheel drive force F _{r_c} in a decreasing direction to make the corrected pitch rate ω _{_c} ^* a positive value (nose up). In particular, when the antidive angle φ is positive and the vehicle 100 is in an accelerating state (required acceleration a _fr > 0), the pitch rate adjuster 56 of this embodiment sets the corrected pitch rate ω _{_c} ^* to a negative value to reduce the pitch angle _θ . Furthermore, in the present embodiment, when the anti-dive angle φ is positive and the vehicle 100 is in a decelerating state (required acceleration a _fr < 0), the pitch rate adjustment unit 56 determines the corrected pitch rate ω _{_c} ^* so as to increase the pitch angle θ by setting the rear wheel driving force F _r to a negative value.

Then, the pitch rate adjustment unit 56 outputs a corrected front wheel driving force _{Ff_c} and a corrected rear wheel driving force Fr_c to the front wheel inverter 12f and the rear wheel inverter 12r, respectively, under predetermined conditions described below when the vehicle 100 is accelerating or decelerating. On the other hand, the pitch rate adjustment unit 56 outputs a basic front wheel driving force _{Ff_b} and a basic rear wheel driving force _{Fr_b} to the front wheel inverter 12f and the rear wheel inverter 12r, respectively, under conditions other than the above-mentioned _{predetermined} conditions.

The driving force control method of this embodiment, including the pitch rate adjustment process, is described in further detail below.

Figure 4 is a flowchart explaining the driving force control method of this embodiment. The controller 50 (particularly the pitch rate adjustment unit 56) repeatedly executes the routine shown in the flowchart of Figure 4 at a predetermined calculation period.

As shown, the controller 50 of this embodiment performs the following operations based on various input information: determining whether the vehicle 100 is operating under automatic driving (step S1000); determining whether the acceleration fluctuation (rate of change in longitudinal acceleration a) is equal to or greater than a certain value (step S1100); determining whether the steering angle of the vehicle 100 is equal to or less than a certain value (step S1200); determining whether the road surface gradient of the vehicle 100 is equal to or less than a certain value (step S1300); and determining whether the friction (road surface μ) of the road surface on which the vehicle 100 is traveling is equal to or greater than a certain value (step S1400).

Then, when the determination results of both steps S1000 and S1100 are positive, the controller 50 executes the processes of steps S1200 and after. On the other hand, when the determination results of steps S1000 or S1100 are negative, the controller 50 sets the pitch rate ω to the basic pitch rate _{ω_b} ^* (step S1700).

Furthermore, when all of the determination results of steps S1200 to S1400 are positive, the controller 50 sets the corrected pitch rate ω _{_c} ^* to the first corrected pitch rate ω _{_c1} ^* . On the other hand, when at least one of the determination results of these determinations is negative, the controller 50 sets the corrected pitch rate ω _{_c} ^* to the second corrected pitch rate ω _{_c2} ^* . Details of the first corrected pitch rate ω _{_c1} ^* and the second corrected pitch rate ω _{_c2} ^* will be described below.

Fig. 5 is a map for explaining an example of operating points of the vehicle 100 when the first corrected pitch rate ω _{_c1} ^* is set. In this map, a set of operating points determined according to each distribution ratio κ is represented by a dashed line. That is, each dashed line represents a set of operating points of a constant pitch rate ω determined according to each distribution ratio κ. In particular, a specific value of the distribution ratio κ (e.g., 50:50) is described in Fig. 5 for the purpose of aiding understanding, but is not intended to limit the configuration of this embodiment.

As can be seen from Fig. 5, the first corrected pitch rate ω _{_c1} ^* is set so as to generate a pitch force to counteract the inertial force acting on the occupant depending on the acceleration/deceleration (positive or negative longitudinal acceleration a) of the vehicle 100. More specifically, when the vehicle 100 accelerates and an inertial force acts on the occupant in a direction pressing the occupant against the seat, the first corrected pitch rate ω _c1 * is determined so as to reduce the pitch angle θ (so as to pitch the vehicle 100 nose down) in order to generate a pitch force in a direction to counteract ^this (a pitch force in a direction moving the occupant away from the _seat ) (see (i) in Fig. 5).

On the other hand, when the vehicle 100 decelerates due to an inertial force acting in a direction moving the occupant away from the seat, the first corrected pitch rate ω _{_c1} * is determined to increase the pitch angle θ (to move the vehicle 100 nose-up) in order to generate a pitch force that counteracts this inertial force (a pitch force that presses the occupant against ^{the seat)} (see (ii) of Figure 5).

Next, a further detailed description will be given of the control result in the case where the first corrected pitch rate ω _{_c1} ^* is set during acceleration of the vehicle 100, with reference to the time chart in Fig. 6. In particular, Fig. 6(A) shows the change over time of the longitudinal acceleration a, and Fig. 6(B) shows the change over time of the pitch angle θ.

As shown in the figure, the first corrected pitch rate ω _{_c1} ^* is set at time t1 before the timing (time t2) at which acceleration of the vehicle 100 is detected, so that the pitch angle θ decreases (nose down) in response to an increase in the longitudinal acceleration a.

In particular, in this embodiment, the control to reduce the pitch angle θ is started before time t2 when acceleration actually starts. This allows the occupants of the vehicle 100 to recognize the change in pitch angle θ prior to the actual change in the longitudinal acceleration a. Therefore, compared to the case where the pitch angle θ is reduced after time t2 when the longitudinal acceleration a actually starts to change (dashed line graph in FIG. 6), the occupants can be made aware that a change in the longitudinal acceleration a will occur, and can be encouraged to prepare for that change.

FIG. 7 is a diagram for explaining the control result in the case where the first corrected pitch rate ω _{— c1} ^* is set when the vehicle 100 is decelerating.

As shown in the figure, the first corrected pitch rate ω _{_c1} ^* is set at time t1, which is before the timing (time t2) at which deceleration of the vehicle 100 is detected, so that the pitch angle θ increases (nose up) in accordance with the decrease in the longitudinal acceleration a.

In particular, in the example shown in FIG. 7, the control to increase the pitch angle θ is started before time t2, when deceleration actually begins. This allows the occupants of the vehicle 100 to be made aware in advance that a change in the longitudinal acceleration a will occur, and encourages them to prepare for that change.

Next, the second corrected pitch rate ω _{_c2} ^* will be described. The second corrected pitch rate ω _{_c2} ^* is set when any one of the determination results in steps S1200 to S1400 is negative. In particular, the second corrected pitch rate ω _{_c2} ^* is set so that the amount of decrease in the pitch angle θ is suppressed compared to the first corrected pitch rate ω _{_c1} ^* .

In particular, when the steering angle exceeds a certain value (No in step S1200), the controller 50 sets the pitch rate ω to the second corrected pitch rate ω _{_c2} ^* . In particular, the absolute value of the second corrected pitch rate ω _{_c2} ^* is set to a smaller value as the steering angle increases.

As a result, when the vehicle 100 is turning and the steering angle becomes large, the pitch displacement is suppressed according to the magnitude of the steering angle (degree of turning), making it possible to avoid so-called oversteer or understeer.

Furthermore, when the gradient angle exceeds a certain value (No in step S1300), the controller 50 sets the pitch rate ω to the second corrected pitch rate ω _{_c2} ^* . In particular, the absolute value of the second corrected pitch rate ω _{_c2} ^* is set to a smaller value as the gradient angle increases.

As a result, when the vehicle 100 is traveling uphill, the pitch displacement is suppressed according to the magnitude of the gradient angle (the degree of inclination of the uphill road), making it possible to prevent the vehicle 100 from moving forward or backward unintentionally due to the gradient.

Furthermore, when the friction (road surface μ) of the road is less than a certain value (No in step S1400), the controller 50 sets the pitch rate ω to the second corrected pitch rate ω _{_c2} ^* . In particular, the absolute value of the second corrected pitch rate ω _{_c2} ^* is set to a smaller value as the road surface μ decreases.

As a result, when the vehicle 100 is traveling on a slippery road surface, the pitch displacement can be suppressed according to the smallness of the road surface μ (slipperiness), thereby preventing the vehicle 100 from slipping.

Fig. 8 is a time chart showing an example of a control result when the second corrective pitch rate ω _{_c2} ^* is applied. In Fig. 8, for reference, the time-dependent changes in the pitch angle θ when the first corrective pitch rate ω _{_c1} ^* and the basic pitch rate ω _{_b} ^* are applied are partially shown by a dashed line and a broken line, respectively.

As shown in the figure, according to the control of this embodiment, when it is detected that the steering angle of the vehicle 100 is equal to or greater than a certain value (time t3), the second corrective pitch rate ω _{_c2} ^* is set as the target value of the pitch rate ω in the pitch rate adjustment process according to the increase in the longitudinal acceleration a during the detection. This reduces the control amount of the pitch angle θ compared to when the first corrective pitch rate ω _{_c1} ^* is set. Similarly, when it is detected that the gradient angle is equal to or greater than a certain value (time t4), the second corrective pitch rate ω _{_c2} ^* is set in the pitch rate adjustment process according to the increase in the longitudinal acceleration a during the detection, and the control amount of the pitch angle θ is reduced. Furthermore, when it is detected that the road surface μ is less than a certain value (time t5), the second corrective pitch rate ω _{_c2} ^* is set in the pitch rate adjustment process according to the increase in the longitudinal acceleration a during the detection, and the control amount of the pitch angle θ is reduced.

The effects of the configuration of this embodiment described above are explained in more detail below.

In this embodiment, a driving force control method is provided that controls the driving force distribution (Ff, Fr) to the front wheel motor 10f as a first driving source connected to the front wheels 11f and the rear wheel motor 10r as a second driving source connected to the rear wheels 11r so that the pitch angle θ of the vehicle 100 behaves as desired. In this driving force control method, a pitch rate adjustment process (step _S1500 or step _S1600 ) is executed to adjust the pitch rate _ω based on a required acceleration _afr for the vehicle 100 so as to generate a pitch displacement in a direction that cancels the longitudinal acceleration a corresponding to the required acceleration afr. In the pitch rate adjustment process, the pitch rate ω is adjusted by controlling the driving force of the front wheel motor 10f (front wheel driving force _Ff ) and the driving force of the rear wheel motor 10r (rear wheel driving force _Fr ) in different directions.

In this way, by controlling the positive/negative relationship between the front wheel drive force _Ff and the rear wheel drive force _Fr so as to realize the adjusted pitch rate ω, it is possible to suppress the inertial force in the longitudinal direction acting on the occupant due to acceleration/deceleration in the longitudinal direction, and to suppress shaking of the head of the occupant in the pitch direction. Therefore, a control logic for driving force distribution that can suppress car sickness of the occupant is realized without using a complicated mechanical structure.

In particular, in this embodiment, the pitch rate adjustment process is executed after a command to change the required acceleration _afr is issued (after time t1 in FIG. 6 or FIG. 7) and before the timing at which the longitudinal acceleration a actually changes (time t2).

This allows the occupants of the vehicle 100 to recognize the change in pitch angle θ prior to the actual change in the longitudinal acceleration a, thereby making them aware that a change in the longitudinal acceleration a will occur. This allows the occupants to be given an opportunity to prepare in advance for the change in the longitudinal acceleration a, thereby reducing the impact on the occupants of the change in the longitudinal acceleration a.

In particular, in the pitch rate adjustment process, when the longitudinal acceleration a is positive (when the vehicle 100 is accelerating), the rear wheel drive force _Fr is set negative to make the pitch rate ω a negative value, and when the longitudinal acceleration a is negative (when the vehicle 100 is decelerating), the front wheel drive force _Ff is set negative to make the pitch rate ω a positive value. For convenience, this control logic is also referred to as the "first pitch control" below.

This realizes a specific control mode for appropriately decreasing or increasing the pitch angle θ in response to the longitudinal acceleration a for a vehicle 100 that has a structure in which the anti-dive angle φ is positive.

Furthermore, in the pitch rate adjustment process, when the longitudinal acceleration a is positive (when the vehicle 100 is accelerating), the front wheel drive force _Ff is set negative to make the pitch rate ω a negative value, and when the longitudinal acceleration a is negative (when the vehicle 100 is decelerating), the rear wheel drive force _Fr is set negative to make the pitch rate ω a positive value. For convenience, hereinafter, this control logic is also referred to as "second pitch control."

This realizes a specific control mode for appropriately decreasing or increasing the pitch angle θ in response to the longitudinal acceleration a for a vehicle 100 having a structure in which the anti-dive angle φ is negative.

Furthermore, in the pitch rate adjustment process, when the anti-dive angle φ of the suspension on the front side of the vehicle 100 is positive, if the longitudinal acceleration a is positive, the rear wheel driving force _Fr is set negative to make the pitch rate ω a negative value, and if the longitudinal acceleration a is negative, the front wheel driving force _Ff is set negative to make the pitch rate ω a positive value. On the other hand, when the anti-dive angle φ of the suspension on the front side of the vehicle 100 is negative, if the longitudinal acceleration a is positive, the front wheel driving force _Ff is set negative to make the pitch rate ω a negative value, and if the longitudinal acceleration a is negative, the rear wheel driving force _Fr is set negative to make the pitch rate ω a positive value.

This allows for a specific control mode to be realized for achieving an appropriate decrease or increase in pitch angle θ in response to longitudinal acceleration a, regardless of whether the vehicle 100 has a positive or negative anti-dive angle φ. In other words, it is possible to realize a general-purpose control logic for pitch angle θ that can be used for both vehicles 100 with positive and negative anti-dive angles φ.

In addition, in this embodiment, the absolute value of the pitch rate ω is made smaller as the steering angle of the vehicle 100 increases, as the gradient angle of the vehicle 100 increases, and/or as the friction of the road on which the vehicle 100 is traveling decreases.

This makes it possible to prevent the occurrence of a situation in which the behavior of the pitch angle θ, depending on the driving environment of the vehicle 100, deviates excessively from the behavior of the basic pitch angle θ _{_b} ^*, which is determined taking into account the vehicle characteristics, even under the pitch rate adjustment process.

In addition, when the vehicle 100 is operating by automatic driving, a pitch rate adjustment process is executed, and when the vehicle 100 is operating by manual driving operation, the pitch rate ω is set to a predetermined basic pitch rate ω _{_b} ^* (step S1700). Then, the basic pitch rate ω _{_b} ^* is determined according to a basic driving force distribution (basic distribution ratio κ _b ) that is determined from the viewpoint of obtaining desired vehicle characteristics based on the required acceleration a _fr for the vehicle 100.

This makes it possible to realize control of the pitch angle θ that can suppress shaking of the occupant's head in the pitch direction during automatic driving. In particular, during automatic driving, the change command of the required acceleration a _fr is not directly linked to the driver's operation (such as operation on the accelerator pedal). For this reason, it is assumed that during automatic driving, it is difficult for the occupant to predict the change in the longitudinal acceleration a. Therefore, by executing the pitch rate adjustment process that changes the pitch angle θ to the basic pitch angle θ _{_b} ^* only in this case, it is possible to suitably suppress the shaking of the occupant's body caused by the change in the longitudinal acceleration a that is unexpected for the occupant. On the other hand, during manual driving operation in which the occupant can easily predict the change in the longitudinal acceleration a, it is possible to control the pitch rate ω after more appropriately predicting the change in the longitudinal acceleration a. On the other hand, in a scene in which the change in the longitudinal acceleration a is difficult to predict, the behavior of the vehicle 100 can be stabilized by executing the control of the pitch rate ω that emphasizes the vehicle characteristics.

Furthermore, in this embodiment, a controller 50 is provided as a driving force control device for executing the above driving force control method.

In particular, the controller 50 functions as a driving force control device that controls the driving force distribution (Ff, Fr) to the front wheel motor 10f as a first driving source connected to the front wheels 11f and the rear wheel motor 10r as a second driving source connected to the rear wheels 11r so that the pitch angle θ of the vehicle 100 behaves as desired. The controller 50 includes a pitch rate adjustment unit (step _S1500 or step _S1600 ) that adjusts the pitch rate _ω based on a required acceleration _afr for the vehicle 100 so as to generate a pitch displacement in a direction that cancels the longitudinal acceleration a corresponding to the required acceleration afr. The pitch rate adjustment unit adjusts the pitch rate ω by controlling the driving force of the front wheel motor 10f (front wheel driving force _Ff ) and the driving force of the rear wheel motor 10r (rear wheel driving force _Fr ) in different directions.

This allows for a control device configuration that is suitable for executing the above-mentioned driving force control method.

The above describes embodiments of the present invention, but the above embodiments merely show some examples of applications of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

For example, in the above embodiment, an example was described in which the controller 50 (pitch rate adjustment unit 56) is configured to be able to selectively execute the first pitch control and the second pitch control by referring to the antidive angle φ determined from the structure of the vehicle 100. However, this is not limited to this, and the controller 50 may be configured to be able to execute only one of the first pitch control and the second pitch control. In this way, by using a controller 50 that implements control logic for the pitch angle θ appropriate for the positive/negative antidive angle φ of the vehicle 100 that is known in advance, the effects substantially expected in the driving force control method of this embodiment can be obtained, and the program implemented in the controller 50 can also be simplified.

REFERENCE SIGNS LIST 10 Drive motor 10f Front wheel motor 10r Rear wheel motor 11f Front wheel 11r Rear wheel 12f Front wheel inverter 12r Rear wheel inverter 50 Controller 52 Total required driving force calculation unit 53 Basic driving force distribution unit 55 Required jerk calculation unit 56 Pitch rate adjustment unit 100 Vehicle

Claims (8)

1. A driving force control method for controlling a driving force distribution to a first driving source connected to front wheels and a second driving source connected to rear wheels such that a pitch angle of a vehicle behaves as desired, comprising:
execute a pitch rate adjustment process for adjusting a pitch rate based on a required acceleration for the vehicle so as to generate a pitch displacement in a direction that cancels the longitudinal acceleration corresponding to the required acceleration;
the pitch rate adjustment process adjusts the pitch rate by controlling the drive force distribution so that the drive force of the first drive source and the drive force of the second drive source are different in positive and negative from each other;
The pitch rate adjustment process is executed after a command to change the required acceleration is issued and before the longitudinal acceleration actually changes.
Driving force control method. 2. A driving force control method according to claim 1 ,
In the pitch rate adjustment process,
When the longitudinal acceleration is positive, the driving force of the second driving source is set to negative, thereby making the pitch rate a negative value.
when the longitudinal acceleration is negative, the driving force of the first driving source is set to a negative value, thereby making the pitch rate a positive value.
Driving force control method. 2. A driving force control method according to claim 1 ,
In the pitch rate adjustment process,
When the anti-dive angle of the suspension on the front side of the vehicle is positive,
When the longitudinal acceleration is positive, the driving force of the second driving source is set to negative, thereby making the pitch rate a negative value.
When the longitudinal acceleration is negative, the driving force of the first driving source is set to a negative value, thereby making the pitch rate a positive value;
If the anti-dive angle is negative,
When the longitudinal acceleration is positive, the driving force of the first driving source is set to negative, thereby making the pitch rate a negative value;
When the longitudinal acceleration is negative, the driving force of the second driving source is set to a negative value, thereby making the pitch rate a positive value.
Driving force control method. The driving force control method according to any one of claims 1 to 3 ,
Furthermore, the absolute value of the pitch rate is made smaller as the steering angle of the vehicle increases.
Driving force control method. The driving force control method according to any one of claims 1 to 4 ,
Furthermore, the greater the gradient angle of the road on which the vehicle is traveling, the smaller the absolute value of the pitch rate is set.
Driving force control method. A driving force control method according to any one of claims 1 to 5 ,
Furthermore, the absolute value of the pitch rate is made smaller as the friction of the road on which the vehicle runs is smaller.
Driving force control method. A driving force control method according to any one of claims 1 to 6 ,
executing the pitch rate adjustment process when the vehicle is operating in an autonomous driving mode;
setting the pitch rate to a predetermined base pitch rate when the vehicle is being manually operated;
determining the basic pitch rate in accordance with a basic driving force distribution determined from the viewpoint of obtaining a desired vehicle characteristic based on a required acceleration for the vehicle;
Driving force control method. A driving force control device that controls a driving force distribution to a first driving source connected to a front wheel and a second driving source connected to a rear wheel so that a pitch angle of a vehicle behaves as desired, comprising:
a pitch rate adjustment unit that adjusts a pitch rate based on a required acceleration for the vehicle so as to generate a pitch displacement in a direction that cancels out a longitudinal acceleration corresponding to the required acceleration,
The pitch rate adjustment unit is
adjusting the pitch rate by controlling the drive force distribution so that the drive force of the first drive source and the drive force of the second drive source are different in sign from each other;
The pitch rate adjustment is performed after a command for changing the required acceleration is issued and before the longitudinal acceleration actually changes.
Driving force control device.

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