Driving force control method and driving force control device

Abstract

The present invention provides a driving force control method, which is executed in a vehicle having a first motor for driving the front wheels and a second motor for driving the rear wheels. The driving force requested for driving is distributed at a prescribed distribution ratio according to the driving state of the vehicle and output by the first motor and the second motor. In this driving force control method, according to the change in the distribution ratio based on the driving state of the vehicle, the output torque is shifted from one motor to the other motor, and a slip state parameter indicating the slip state of the vehicle is set. When the slip state parameter is below a prescribed threshold value, the upper limit of the change speed of the shifted output torque is set to a relatively small first upper limit value, and when the slip state parameter exceeds the threshold value, the upper limit of the change speed is set to a relatively large second upper limit value.

Description

Technical Field

[0001] The present invention relates to a driving force control method and a driving force control device. Background Art

[0002] In JP5835583B, a driving force control method in a four-wheel drive electric vehicle in which a front wheel can be driven by a first motor and a rear wheel can be driven by a second motor in an electric vehicle having an electric motor as a driving source for traveling is proposed.

[0003] In this driving force control method, the slip states of the front wheels and the rear wheels are detected based on the rotational speed difference between the front wheels and the rear wheels, and the output torques of the first motor and the second motor are changed based on the slip states, so that the output torque moves from the slipping wheel to the non-slipping wheel among the front wheels and the rear wheels. Further, when the output torque moves, the change speed of the moving amount of the output torque is limited to be equal to or less than a first specified value at which the non-slipping wheel does not slip.

[0004] The inventors of the present invention have found that in the driving force control method of JP5835583B, during the communication between the respective inverters of the first motor and the second motor and the control device, due to reasons such as the phase shift of the signals sent to the respective inverters, the control responsiveness between the first motor and the second motor is different.

[0005] Therefore, the responsiveness of the actual torque in the first motor with respect to the torque command value is different from the responsiveness of the actual torque in the second motor with respect to the torque command value, and when the above output torque moves, a state in which the total required driving force of the vehicle is temporarily not satisfied occurs, and a change in the longitudinal G (longitudinal acceleration) that causes discomfort to the occupants is generated. Summary of the Invention

[0006] Therefore, an object of the present invention is to provide a driving force control method and a driving force control device capable of suppressing a change in the longitudinal G (longitudinal acceleration) when the output torque moves.

[0007] According to one aspect of the present invention, there is provided a driving force control method that is executed in a vehicle including a first motor that drives a front wheel and a second motor that drives a rear wheel, and distributes a required driving force for traveling at a prescribed distribution ratio according to the traveling state of the vehicle and outputs the required driving force through the first motor and the second motor. In this driving force control method, according to a change in the distribution ratio based on the traveling state of the vehicle, the output torque is moved from one motor to the other motor, a slip state parameter indicating the slip state of the vehicle is set, and when the slip state parameter is equal to or less than a prescribed threshold value, the upper limit of the change speed of the moving output torque is set to a relatively small first upper limit value, and when the slip state parameter exceeds the threshold value, the upper limit of the change speed of the moving output torque is set to a relatively large second upper limit value. Description of the Drawings

[0008] Figure 1 It is a diagram showing the structure of a vehicle for explaining a driving force control method according to an embodiment of the present invention.

[0009] Figure 2 It is a block diagram showing the structure of a driving force control device according to a first embodiment.

[0010] Figure 3 It is a flowchart showing the processing in a speed limit section.

[0011] Figure 4 It is a timing diagram showing the aging change of the post - limit torque change amount.

[0012] Figure 5 It is a diagram showing the control result of the driving force control method according to the present embodiment.

[0013] Figure 6 It is a diagram showing the control result of a comparative example.

[0014] Figure 7 It is a block diagram showing the structure of a driving force control device according to a second embodiment. Detailed Description of the Embodiments

[0015] Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings.

[0016] [First Embodiment]

[0017] Hereinafter, the first embodiment will be described.

[0018] Figure 1 It is a diagram showing the structure of a vehicle 100 for explaining a driving force control method according to the present embodiment.

[0019] In addition, as the vehicle 100 of the present embodiment, an electric vehicle or a hybrid vehicle etc. equipped with a drive motor 10 as a drive source and capable of traveling by the driving force of the drive motor 10 is assumed.

[0020] In the vehicle 100, a front motor 10f as a first motor for driving the front wheels 11f is provided at a front position (hereinafter referred to as "front - wheel side"), and a rear motor 10r as a second motor for driving the rear wheels 11r is provided at a rear position (hereinafter referred to as "rear - wheel side"). In particular, the vehicle 100 of the present embodiment adopts a structure in which the drive system on the front - wheel side and the drive system on the rear - wheel side are mechanically independent of each other.

[0021] The front motor 10f is configured as a three-phase AC motor. The front motor 10f receives power from a battery 15 as a power source to generate driving force. The driving force generated by the front motor 10f is transmitted to the front wheel 11f via the front transmission 16f and the front drive shaft 21f. In addition, the front motor 10f converts the regenerative driving force generated when the front motor 10f rotates in conjunction with the front wheel 11f when the vehicle 100 is running into AC power. In addition, the power supplied to the front motor 10f is regulated by the front inverter 12f. In particular, the front inverter 12f is based on the front torque T fm The final command value (hereinafter also referred to as the "final front torque command value T**) fm ”), adjusting the driving force generated by the front motor 10f.

[0022] On the other hand, the rear motor 10r is configured as a three-phase AC motor. The rear motor 10r receives power supply from the battery 15 as a power source to generate driving force. The driving force generated by the rear motor 10r is transmitted to the rear wheel 11r via the rear transmission 16r and the rear drive shaft 21r. In addition, the rear motor 10r converts the regenerative driving force generated when the rear motor 10r rotates in conjunction with the rear wheel 11r when the vehicle 100 is running into AC power. In addition, the power supplied to the rear motor 10r is regulated by the rear inverter 12r. In particular, the rear inverter 12r is based on the rear torque T mr The final command value (hereinafter also referred to as the "final torque command value T**) mr ”), adjusting the driving force generated by the rear motor 10r.

[0023] Furthermore, the vehicle 100 is provided with a controller 50 as a driving force control device. The controller 50 controls the output torque of the front motor 10f (hereinafter also referred to as “front torque T fm ”) and the output torque of the rear motor 10r (hereinafter also referred to as “rear torque T mr ”).

[0024] The controller 50 is composed of a computer having 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 various processes in the vehicle control described below. In particular, the functions of the controller 50 are implemented by any on-vehicle 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. In addition, the controller 50 can be implemented by a single computer hardware, or can be implemented by distributing various processes by using a plurality of computer hardware.

[0025] Specifically, the controller 50 acquires the vehicle speed V, the accelerator opening APO, the rotational speed of the front wheel 11f determined based on the rotational speed of the front motor 10f (hereinafter also referred to as "front wheel speed w f "), and the rotational speed of the rear wheel 11r determined based on the rotational speed of the rear motor 10r (hereinafter also referred to as "rear wheel speed w r ") as input information. Moreover, based on these input information, the controller 50 calculates the final front torque command value T** fm and the final rear torque command value T** mr , and outputs them to the front inverter 12f and the rear inverter 12r, respectively.

[0026] The vehicle speed V as the input information can be acquired, for example, as the detection value of a vehicle speed sensor (not shown), or can be estimated based on at least any one of the front wheel speed w f and the rear wheel speed w r . In addition, the accelerator opening APO can be acquired, for example, as the detection value of an accelerator opening sensor (not shown). The accelerator opening APO corresponds to the operation amount of the accelerator pedal by the driver of the vehicle 100. In addition, when the vehicle 100 is equipped with a so-called autonomous driving function, as the accelerator opening APO, the operation amount of the accelerator pedal corresponding to the command from the autonomous driving controller, or any other parameter indicating the magnitude of the requested driving force can be adopted. Furthermore, the front wheel speed w f and the rear wheel speed w r can be acquired, for example, as the detection values of a rotational speed sensor (not shown). Hereinafter, the driving force control executed by the controller 50 will be described in detail.

[0027] Figure 2 is a block diagram showing the structure of the controller 50. As shown in the figure, the controller 50 includes: a total requested torque calculation unit 52, a torque distribution unit 53, a slip control unit 54, a rate limiter 56, an adder 58, and a subtractor 60.

[0028] The total requested torque calculation unit 52 calculates the total torque corresponding to all the driving forces requested for the vehicle 100, that is, the total requested torque T* mfr , which is the sum of the torques requested for both the front motor 10f and the rear motor 10r as the drive sources, based on the vehicle speed V and the accelerator opening APO.

[0029] Specifically, in the present embodiment, the total requested torque T* mfr corresponds to the target value of the total driving force, which is the sum of the driving forces to be output by the front wheel 11f and the driving forces to be output by the rear wheel 11r. For example, the total requested torque calculation unit 52 reads out from an arbitrary memory the total requested torque T* mfrThe specified mapping diagram can calculate the total requested torque T* by applying the current vehicle speed V and the accelerator opening APO to this mapping diagram. mfr Then, the total requested torque calculation unit 52 outputs the calculated total requested torque T* mfr to the torque distribution unit 53 and the subtraction unit 60 respectively.

[0030] The torque distribution unit 53 takes the total requested torque T* from the total requested torque calculation unit 52 mfr as input and calculates the basic rear torque command value T mr0 . Specifically, the torque distribution unit 53 multiplies the total requested torque T* mfr by the distribution ratio κ to obtain the basic rear torque command value T mr0 . Here, the distribution ratio κ is the basic target value of the ratio of the rear torque T mr to the front torque T fm . The distribution ratio κ is set to an appropriate value corresponding to the driving state of the vehicle 100. In addition, among the driving states of the vehicle 100 used to determine this distribution ratio κ, it includes the driving mode set for the vehicle 100 (such as a driving mode that emphasizes driving stability or a driving mode that prioritizes energy efficiency) and changes in the center of gravity position of the vehicle 100, etc. For example, the distribution ratio κ is obtained in advance through experiments or simulations, etc., and can be obtained using a mapping diagram with appropriate values determined according to parameters representing the driving state of the vehicle 100 (the total requested torque T* mfr , or the vehicle speed V, etc.). Then, the torque distribution unit 53 outputs the calculated basic rear torque command value T mr0 to the rate limiter 56.

[0031] The slip control unit 54 takes the front wheel speed w f and the rear wheel speed w r as input, sets the slip control intervention flag f FB , and calculates the feedback correction torque T FB .

[0032] Specifically, the slip control unit 54 calculates the feedback correction torque T FB so that the deviation between the front wheel speed w f and the rear wheel speed w r (hereinafter also referred to as "front - rear wheel speed difference Δw mfr ") is below the specified front - rear wheel speed difference threshold Δw mfr_Th . In addition, the front - rear wheel speed difference threshold Δw mfr_Th is determined to be the value of the difference between the front wheel speed w f and the rear wheel speed w r that serves as the benchmark for estimating the slip state of the vehicle 100 (the state where the front wheel 11f or the rear wheel 11r slips).

[0033] Furthermore, when the speed difference Δw between the front and rear wheels mfr exceeds the speed difference threshold Δw between the front and rear wheels mfr_Th (i.e., when the calculated feedback correction torque T FB is not substantially 0), the slip control unit 54 sets the slip control intervention flag f FB to "1". On the other hand, when the speed difference Δw between the front and rear wheels mfr is less than or equal to the speed difference threshold Δw between the front and rear wheels mfr_Th (i.e., when the calculated feedback correction torque T FB is substantially 0), the slip control unit 54 sets the slip control intervention flag f FB to "0".

[0034] That is, in the present embodiment, the case where the slip control intervention flag f FB is set to "1" corresponds to the case where the vehicle 100 is in a slip state (a state where the front wheel 11f or the rear wheel 11r slips). On the other hand, the case where the slip control intervention flag f FB is set to "0" corresponds to the case where the vehicle 100 is in a non-slip state (a state where neither the front wheel 11f nor the rear wheel 11r slips). Then, the slip control unit 54 outputs the calculated feedback correction torque T FB and the set slip control intervention flag f FB to the rate limiting unit 56.

[0035] The rate limiting unit 56 uses the distribution ratio κ and the basic rear torque command value T mr0 from the torque distribution unit 53, as well as the feedback correction torque T FB and the slip control intervention flag f FB from the slip control unit 54 as inputs, and calculates the limited movement torque amount ΔT** m_lim . The processing in the rate limiting unit 56 will be described in detail below.

[0036] Figure 3 is a flowchart showing the processing in the rate limiting unit 56. In addition, the program shown in this flowchart is repeatedly executed by the controller 50, for example, triggered by turning on the power supply of the vehicle 100 and at each prescribed operation cycle.

[0037] In step S100, the rate limiting unit 56 calculates the movement torque amount ΔT* m . Here, the movement torque amount ΔT* m is a value corresponding to the output torque that moves from the rear wheel 11r to the front wheel 11f according to the distribution ratio κ and the feedback correction torque T FB . In particular, the movement torque amount ΔT* mIt takes a positive value when making positive torque move from the front motor 10f to the rear motor 10r, and takes a negative value when making positive torque move from the rear motor 10r to the front motor 10f.

[0038] Specifically, first, the rate limiting unit 56 calculates the corrected rear torque T* mr0 by taking the sum of the basic rear torque command value T FB and the value obtained by multiplying the feedback correction torque T FB by the distribution ratio κ (which is equivalent to the distribution amount of the feedback correction torque T mr for the rear motor 10r). That is, the corrected rear torque T* mr is the value obtained by correcting the basic rear torque command value T mr0 in consideration of the slip state of the vehicle 100. Then, the rate limiting unit 56 calculates the moving torque amount ΔT* mr as the value obtained by subtracting the previous value from the current value of the corrected rear torque T* m .

[0039] Next, in step S110, the rate limiting unit 56 calculates the change speed C m of the moving torque amount ΔT* r . Specifically, the rate limiting unit 56 calculates the value obtained by dividing the moving torque amount ΔT* m by the operation period as the change speed C r .

[0040] In step S120, the rate limiting unit 56 determines whether the slip control intervention flag f FB is set to "0" (whether the vehicle 100 is in a non-slip state). Then, when it is determined that the slip control intervention flag f FB is set to "0", the rate limiting unit 56 executes the processing after step S130.

[0041] In step S130, the rate limiting unit 56 sets the first upper limit value C r_lim1 as the upper limit value of the change speed C r . Here, the first upper limit value C r_lim1 is the upper limit value of the change speed C r determined from the viewpoint of suppressing the delay of torque control caused by the difference in responsiveness in the communication (CAN communication) between one controller 50 and each of the front inverter 12f and the rear inverter 12r when the vehicle 100 is in a non-slip state.

[0042] Furthermore, in step S140, the rate limiting unit 56 is based on the change speed C r calculated in step S110 and the first upper limit value C r_lim1to calculate the first limited movement torque amount ΔT* m_lim1 . Specifically, the speed limiting unit 56 selects the change speed C r and the smaller one of the first upper limit value C r_lim1 , and adds the previous value of the movement torque amount ΔT* m to the selected value, thereby calculating the first limited movement torque amount ΔT* m_lim1 .

[0043] On the other hand, when it is determined in the above step S120 that the slip control intervention flag f FB is not set to "0" (i.e., is set to "1"), the speed limiting unit 56 performs the processing after step S150.

[0044] In step S150, the speed limiting unit 56 sets the second upper limit value C r_lim2 as the upper limit value of the change speed C r . Here, the second upper limit value C r_lim2 is the upper limit value of the change speed C m determined from the viewpoint of suppressing a sharp change in the movement torque amount ΔT* r when the vehicle 100 is in a slip state. On the other hand, from the viewpoint of eliminating the slip state of the vehicle 100 as quickly as possible, the second upper limit value C r_lim2 of the present embodiment is set to a value larger than the first upper limit value C r_lim1 set when no slip occurs.

[0045] Furthermore, in step S160, the speed limiting unit 56 calculates the second limited movement torque amount ΔT* r based on the change speed C r_lim2 calculated in step S110 and the second upper limit value C m_lim2 calculated in step S150. r . Specifically, the speed limiting unit 56 selects the smaller one of the current change speed C r_lim2 and the second upper limit value C m , and adds the previous value of the movement torque amount ΔT* m_lim2 to the selected value, thereby calculating the second limited movement torque amount ΔT*

[0046] Then, in step S170, the limited movement torque amount ΔT* m_lim is output to the adder 58. In particular, the speed limiting unit 56 outputs the first limited movement torque amount ΔT* FB as the limited movement torque amount ΔT* m_lim1 when the slip control intervention flag f m_lim is set to "0". On the other hand, when the slip control intervention flag fFB When it is set to "1", the second restricted movement torque amount ΔT* is output m_lim2 As the restricted movement torque amount ΔT* m_lim .

[0047] Return Figure 2 , the adder 58 uses the previous value of the final post-torque command value T** mr and the restricted movement torque amount ΔT* from the rate limiter 56 m_lim as inputs to calculate the final post-torque command value T** mr . Specifically, the adder 58 calculates the final post-torque command value T** m_lim by adding the restricted movement torque amount ΔT* mr to the previous value of the final post-torque command value T** mr . Thus, the final post-torque command value T** whose change speed is adjusted according to whether slip occurs is obtained mr . Then, the adder 58 outputs the calculated final post-torque command value T** mr to the post-inverter 12r and the subtractor 60

[0048] The subtractor 60 uses the total requested torque T* from the total requested torque calculation unit 52 mfr and the final post-torque command value T** from the adder 58 mr as inputs to calculate the final pre-torque command value T** fm . Thus, the final pre-torque command value T** whose change speed is adjusted in the same way as the final post-torque command value T** mr is obtained fm . Then, the subtractor 60 outputs the calculated final pre-torque command value T** fm to the pre-inverter 12f

[0049] Next, the upper limit of the change speed C m of the movement torque amount ΔT* set in this embodiment will be described in more detail r .

[0050] Figure 4 is a timing diagram showing the aging change of the upper limit of the change speed C m of the movement torque amount ΔT* r . As shown in the figure, in this embodiment, the upper limit of the change speed C m of the movement torque amount ΔT* when slip occurs r is set to a relatively large second upper limit value C r_lim2 , and the upper limit of the change speed C m of the movement torque amount ΔT* when no slip occurs rThe upper limit is set to a relatively small first upper limit value C r_lim1 . In particular, in the present embodiment, the second upper limit value C r_lim2 takes a substantially constant value regardless of the magnitude of the total requested torque T* mfr . On the other hand, the first upper limit value C r_lim1 takes a constant value smaller than the second upper limit value C mfr_th in a region below a prescribed torque threshold T r_lim2 determined as a criterion for judging whether it is a low-torque region.

[0051] Thus, in a low-torque region such as when the vehicle 100 decelerates or starts on a low-μ road, and in a scenario where the front wheel 11f or the rear wheel 11r slips, since the relatively large second upper limit value C r_lim2 is set as the upper limit of the change speed C r , the responsiveness of torque control can be maintained at a relatively high level, and the occurring slip can be quickly eliminated.

[0052] On the other hand, in a scenario where no slip occurs even in a low-torque region, the upper limit of the change speed C r is restricted by the relatively small first upper limit value C r_lim1 . Thus, a delay in torque control caused by the difference in communication responsiveness between the above-mentioned controller 50 and the front and rear inverters can be suppressed. More specifically, due to this difference in communication responsiveness, the followability to the command value in the torque control of the front motor 10f and the followability to the command value in the torque control of the rear motor 10r are different from each other, and a situation may occur where the actual total torque T mfr temporarily cannot satisfy the total requested torque T* mfr . In response to this situation, by restricting the upper limit of the change speed C r to the first upper limit value C r_lim1 , the followability of the actual total torque T mfr to the total requested torque T* mfr can be improved.

[0053] Furthermore, the first upper limit value C r_lim1 of the present embodiment is determined such that in a region where the total requested torque T* mfr exceeds the torque threshold T mfr_th , as the total requested torque T* mfr increases more, it increases closer to the second upper limit value C r_lim2 . Therefore, while it is considered that the influence of the difference in the above-mentioned communication responsiveness on torque control becomes smaller, in the high-torque region, by making the first upper limit value C r_lim1 approach the second upper limit value C r_lim2 , it is possible to suppress, together, due to the moving torque amount ΔT* mThe change speed C r The upper limit of r_lim1 is limited by the first upper limit value C, resulting in a decrease in control responsiveness.

[0054] Figure 5 is a diagram showing the control result of the driving force control method of the present embodiment. Additionally, in Figure 6 , as a comparative example, the control result when the driving force control method of the present embodiment is not executed is shown. Additionally, Figure 5 and Figure 6 assume a scenario in a low-torque region such as at the start on a low-μ road, and due to the slip of the rear wheel 11r, the output torque moves from the front wheel 11f to the rear wheel 11r (i.e., the moving torque amount ΔT* m > 0). In particular, in Figure 5 and Figure 6 , it is assumed that the communication responsiveness of the rear inverter 12r to the command signal of the controller 50 is lower than that of the front inverter 12f.

[0055] Figure 6 The difference between the control of the comparative example shown in and the driving force control method of the present embodiment is that the upper limit of the change speed C m of the moving torque amount ΔT* r is always set to the second upper limit value C r_lim2 . In the control of such a comparative example, as can be seen from Figure 6 (B), due to the difference in communication responsiveness between the front wheel side and the rear wheel side as described above, compared with the followability of the actual front torque T f_r to the final front torque command value T** fm , the followability of the actual rear torque T r_r to the final rear torque command value T** mr is low. Therefore, when the change speed C m of the moving torque amount ΔT* r (the inclination of the curve of the final rear torque command value T** mr ) becomes large, the change of the actual rear torque T r_r is delayed relative to the change of the actual front torque T f_r . As a result, when the torque moves, the actual total torque T mfr cannot follow the total requested torque T* mfr , and a front-rear G level difference that causes discomfort to the occupants of the vehicle 100 is generated (refer to the circled part in Figure 6 (A)).

[0056] In contrast, in the control of the present embodiment shown in Figure 5 , the change speed C m of the moving torque amount ΔT* rThe upper limit is restricted to be smaller than the second upper limit value C r_lim2 by the first upper limit value C r_lim1 . Therefore, it is possible to mitigate the difference in the followability of the command value between the actual rear torque T r_r and the actual front torque T f_r (see Figure 5 (B)). As a result, it is possible to suppress the generation of the level difference of the front and rear G during torque movement (see Figure 5 (A)).

[0057] Hereinafter, the operation and effect of the structure of the present embodiment will be described in more detail.

[0058] In the present embodiment, a driving force control method is provided, which is executed in a vehicle 100 having a front motor 10f as a first motor for driving the front wheels 11f and a rear motor 10r as a second motor for driving the rear wheels 11r. The requested driving force (total requested torque T* mfr ) for running is distributed according to a prescribed distribution ratio (distribution ratio κ) based on the running state of the vehicle 100, and is output by the front motor 10f and the rear motor 10r.

[0059] In this driving force control method, according to the change of the distribution ratio γ based on the running state of the vehicle 100, the output torque is shifted from the rear motor 10r as one motor to the front motor 10f as the other motor, and a slip state parameter (front and rear wheel speed difference Δw mfr or a slip control intervention flag f FB ) indicating the slip state of the vehicle 100 is set.

[0060] Moreover, when the slip state parameter is below a prescribed threshold value (when the slip control intervention flag f FB = “0”), the upper limit of the change speed C m of the shifted output torque (shifted torque amount ΔT* r ) is set to a relatively small first upper limit value C r_lim1 . Moreover, when the slip state parameter exceeds the above threshold value (when the slip control intervention flag f FB = “1”), the upper limit of the change speed C m of the shifted torque amount ΔT* r is set to a relatively large second upper limit value C r_lim2 .

[0061] Thus, in a scenario where the actual driving force deviates from the total requested torque T* mfr due to the difference in communication responsiveness in the front and rear drive systems of the vehicle 100, it is possible to make the change speed C m of the shifted torque amount ΔT*r Slows down. Therefore, it is possible to suppress the change in front-rear G caused by the fact that the actual driving force (actual total torque T mfr ) cannot follow the total requested driving force (total requested torque T* mfr ).

[0062] In particular, in the present embodiment, the larger the total requested torque T* mfr , the larger the first upper limit value C r_lim1 is set.

[0063] Accordingly, as the driving force request for the vehicle 100 becomes larger, the change speed C m of the mobile torque amount ΔT* r considering the difference in communication responsiveness in the front-rear drive system is relaxed. Therefore, in a scenario where the influence of the above-mentioned difference in communication responsiveness on torque control is considered to be small, the responsiveness of torque control can be appropriately ensured.

[0064] In addition, when the total requested torque T* mfr is below a prescribed driving force threshold value (torque threshold value T mfr_th ), the first upper limit value C r_lim1 is set to a constant value with respect to the change in the total requested torque T* mfr . On the other hand, when the total requested torque T* mfr exceeds the torque threshold value T mfr_th , the first upper limit value C r_lim1 is set to a variable value that increases as the total requested torque T* mfr increases. In particular, the torque threshold value T mfr_th is determined from the viewpoint of judging the start-up scenario of the vehicle 100.

[0065] Accordingly, it is possible to set an appropriate responsiveness of torque control according to the magnitude of the requested driving force for the vehicle 100.

[0066] Furthermore, in the present embodiment, the above-mentioned slip state parameter includes the rotational speed difference between the front wheels 11f and the rear wheels 11r, that is, the front-rear wheel speed difference Δw mfr , and a prescribed speed difference threshold value (front-rear wheel speed difference threshold value Δw mfr_Th ) is set as the threshold value of the slip state parameter. Moreover, in order to make the front-rear wheel speed difference Δw mfr approach the front-rear wheel speed difference threshold value Δw mfr_Th , the output torque moving from the slipping wheel to the non-slipping wheel among the front wheels 11f and the rear wheels 11r is corrected (the mobile torque amount ΔT* m is corrected to obtain the corrected torque T* m ).

[0067] Thus, based on the front and rear wheel speed difference Δw which is a specific index of whether the front wheel 11f or the rear wheel 11r has slipped mfr the actual slip state of the vehicle 100 can be determined more appropriately. Therefore, the change speed C r can be set to the first upper limit value C r_lim1 or the second upper limit value C r_lim2 .

[0068] In addition, in this embodiment, the final rear torque command value T** which is the torque command value of the rear motor 10r is calculated mr , and the torque command value of the rear motor 10r is determined by limiting the moving torque amount ΔT* r_lim1 by the first upper limit value C r_lim2 or the second upper limit value C m . Then, the final front torque command value T** which is the torque command value of the front motor 10f is calculated by subtracting the final rear torque command value T** mfr from the total requested torque T* mr . In addition, based on the final front torque command value T** fm and the final rear torque command value T** fm , the output torques of the front motor 10f and the rear motor 10r are controlled respectively. mr

[0069] Thus, a specific calculation method is provided to achieve an appropriate balance between suppressing the change of the above-mentioned front and rear G and maintaining the responsiveness related to torque control.

[0070] Furthermore, in this embodiment, a driving force control device for executing the above-mentioned driving force control method is provided.

[0071] The driving force control device (controller 50) is executed in the vehicle 100 having the front motor 10f which is the first motor for driving the front wheel 11f and the rear motor 10r which is the second motor for driving the rear wheel 11r, and distributes the requested driving force for running (total requested torque T* mfr ) at a specified distribution ratio (distribution ratio κ) according to the running state of the vehicle 100, and outputs through the front motor 10f and the rear motor 10r.

[0072] In addition, the controller 50 as the driving force control device has: a torque moving part (rate limiting part 56) which moves the output torque from the rear motor 10r which is one of the motors to the front motor 10f which is the other motor according to the change of the distribution ratio γ based on the running state of the vehicle 100; a slip state parameter setting part (slip control part 54) which sets a slip state parameter (front and rear wheel speed difference Δw mfrand the slip control intervention flag f FB ); and a change speed limiting section (rate limiting section 56) that limits the change speed C of the moving torque amount ΔT* m of r .

[0073] Furthermore, when the slip state parameter is below a specified threshold value (when the slip control intervention flag f FB = "0"), the rate limiting section 56, which is the change speed limiting section, sets the upper limit of the change speed C of the output torque for movement (the moving torque amount ΔT* m ) to a relatively small first upper limit value C r . Further, when the slip state parameter exceeds the above threshold value (when the slip control intervention flag f r_lim1 = "1"), the rate limiting section 56 sets the upper limit of the change speed C of the moving torque amount ΔT* FB to a relatively large second upper limit value C m . r r_lim2 .

[0074] As a result, the structure of an appropriate control device for executing the above-described driving force control method is realized.

[0075] [Second Embodiment]

[0076] Hereinafter, the second embodiment will be described. In addition, the same reference numerals are given to the same elements as those in the first embodiment, and the description thereof will be omitted.

[0077] Figure 7 is a block diagram illustrating the structure of the controller 50 in the present embodiment. As shown in the figure, in the present embodiment, the slip control section 54 is composed of a longitudinal slip control section 54-1 and a lateral slip control section 54-2. The longitudinal slip control section 54-1 performs the same processing as the slip control section 54 in the first embodiment. That is, the longitudinal slip control section 54-1 performs feedback control to suppress the slip of the front wheels 11f or the rear wheels 11r of the vehicle 100.

[0078] On the other hand, the lateral slip control section 54-2 performs control to suppress the slip of the vehicle 100 in the lateral direction (the rotation direction centered on the vehicle center of gravity) that may occur, for example, during a sharp turn. The yaw rate YR detected by a yaw rate sensor (not shown) is input to the lateral slip control section 54-2. Then, the lateral slip control section 54-2 calculates a correction torque T YR determined to eliminate the lateral slip of the vehicle 100 based on the input yaw rate YR.

[0079] In addition, when the calculated correction torque T YR ​When it is above a specified threshold value, the lateral slip control intervention flag f YR is set to "1". Further, when the calculated corrected torque T YR is less than the specified threshold value, the lateral slip control intervention flag f YR is set to "0". Further, the threshold value compared with the corrected torque T YR is set to an appropriate value from the viewpoint of determining whether lateral slip of the vehicle 100 has occurred to such an extent that the total requested torque T* mfr needs to be corrected. Then, the lateral slip control unit 54-2 outputs the calculated corrected torque T YR to the requested torque correction unit 62, and outputs the set lateral slip control intervention flag f YR to the speed limit unit 56.

[0080] The requested torque correction unit 62 uses the total requested torque T* mfr from the total requested torque calculation unit 52 and the corrected torque T YR from the lateral slip control unit 54-2 as inputs to calculate the corrected total requested torque T'* mfr . Then, the requested torque correction unit 62 outputs the calculated corrected total requested torque T'* mfr to the torque distribution unit 53. Therefore, in the calculations after the torque distribution unit 53 described in the first embodiment, the corrected total requested torque T'* mfr is used instead of the total requested torque T* mfr .

[0081] Furthermore, as a flag (slip state parameter) indicating the slip state of the vehicle 100, in addition to the slip control intervention flag f FB , the lateral slip control intervention flag f YR is also input to the speed limit unit 56. Then, in step S120 shown in Figure 3 , when both the slip control intervention flag f FB and the lateral slip control intervention flag f YR are set to "0", the speed limit unit 56 executes the processing after step S130. On the other hand, when at least one of the slip control intervention flag f FB and the lateral slip control intervention flag f YR is set to "1" (when either longitudinal slip or lateral slip of the vehicle 100 has occurred), the speed limit unit 56 executes the processing after step S150.

[0082] Thus, in the speed limit unit 56, not only when longitudinal slip of the vehicle 100 occurs but also when lateral slip occurs, the movement torque amount ΔT*m The change rate C r The upper limit is also set to a relatively large second upper limit value C r_lim2 . Therefore, when the vehicle 100 slides, whether it slides in the front-rear direction or laterally, it is possible to mitigate the moving torque amount ΔT* m The change rate C r limitation, improve the responsiveness of torque control, and quickly eliminate the slide.

[0083] As described above, the embodiments of the present invention have been described. However, the above embodiments merely represent a part of the application examples of the present invention, and do not mean to limit the technical scope of the present invention to the specific structures of the above embodiments.

[0084] For example, in the above embodiment, it is described that the operation is performed by the first upper limit value C r_lim1 or the second upper limit value C r_lim2 to limit the moving torque amount ΔT* m and determine the final rear torque command value T** mr , and subtract the final rear torque command value T** mfr from the total requested torque T* mr to calculate the final front torque command value T** fm . However, it is not limited thereto. For example, the following structure may also be adopted: calculate the final front torque command value T** r_lim1 determined by limiting the moving torque amount ΔT* r_lim2 by the first upper limit value C m or the second upper limit value C fm , and subtract the final front torque command value T** mfr from the total requested torque T* fm to calculate the final rear torque command value T** mr .

[0085] In addition, in the above embodiment, it is described that in the case of performing feedback control for eliminating the sliding state based on the front-rear wheel speed difference Δw mfr (when the slip control intervention flag f FB is set to "1"), the upper limit of the moving torque amount ΔT* m is set to the second upper limit value C r_lim2 . On the other hand, a structure that performs multiple feedback controls for eliminating the sliding state may also be adopted (setting multiple different front-rear wheel speed difference thresholds Δw mfr_Th , and performing different feedback controls corresponding to each front-rear wheel speed difference threshold Δw mfr_Th ), and setting different values of the second upper limit value C r_lim2 corresponding to each type of feedback control to be larger than the first upper limit value C r_lim1within a wide range.

[0086] Furthermore, in the above-described embodiment, it is mainly assumed that the communication responsiveness of the rear inverter 12r to the command signal of the controller 50 is lower than that of the front inverter 12f. However, conversely, even when the communication responsiveness of the rear inverter 12r is lower than that of the front inverter 12f, the control structure described in the above embodiment can be applied in the same manner by switching the positions of the front wheel side and the rear wheel side.

Claims

1. A driving force control method is executed in a vehicle having a first motor for driving the front wheels and a second motor for driving the rear wheels. According to the driving state of the vehicle, a requested driving force for driving is distributed at a prescribed distribution ratio and output by the first motor and the second motor. Among them, According to the change of the distribution ratio based on the driving state of the vehicle, the output torque is moved from one motor to the other motor. A slip state parameter representing the slip state of the vehicle is set. When the slip state parameter is below a prescribed threshold value, the upper limit of the change speed of the moved output torque is set to a relatively small first upper limit value. When the slip state parameter exceeds the threshold value, the upper limit of the change speed is set to a relatively large second upper limit value. The larger the requested driving force is, the larger the first upper limit value is set.

2. The driving force control method according to claim 1, wherein, When the requested driving force is below a prescribed driving force threshold value, the first upper limit value is set to a constant value with respect to the change of the requested driving force. When the requested driving force exceeds the driving force threshold value, the first upper limit value is set to a variable value that increases as the requested driving force increases. The driving force threshold value is determined based on the angle for judging the starting scenario of the vehicle.

3. The driving force control method according to claim 1, wherein, The slip state parameter includes the rotational speed difference between the front wheels and the rear wheels, that is, the front and rear wheel speed difference. A prescribed speed difference threshold value is set as the threshold value. The output torque moving from the slipping wheel to the non-slipping wheel among the front wheels and the rear wheels is corrected so that the front and rear wheel speed difference approaches the speed difference threshold value.

4. The driving force control method according to any one of claims 1 to 3, wherein, The torque command value of the second motor determined by restricting the moved output torque by the first upper limit value or the second upper limit value is calculated. The torque command value of the first motor is calculated by subtracting the torque command value of the second motor from the requested driving force. Based on the torque command value of the first motor and the torque command value of the second motor, the output torques of the first motor and the second motor are controlled respectively.

5. A driving force control device is executed in a vehicle having a first motor for driving the front wheels and a second motor for driving the rear wheels, and distributes a requested driving force for running at a prescribed distribution ratio according to the running state of the vehicle and outputs the driving force through the first motor and the second motor, wherein, The driving force control device has: A torque moving part that moves the output torque from one motor to the other motor according to the change of the distribution ratio based on the driving state of the vehicle; A slip state parameter setting part that sets a slip state parameter representing the slip state of the vehicle; A change speed limiting part that limits the change speed of the moved output torque. When the sliding state parameter is below a specified threshold value, the change speed limiting unit sets the upper limit of the change speed of the moving output torque to a relatively small first upper limit value. When the sliding state parameter exceeds the threshold value, the change speed limiting unit sets the upper limit of the change speed of the moving output torque to a relatively large second upper limit value. The greater the requested driving force, the larger the first upper limit value is set.

Images