Vehicle control device

Abstract

To provide a control device for a vehicle which suppresses slip of a wheel at the vehicle start time.SOLUTION: A control device for a vehicle includes: a first traveling motor connected with a first wheel; a second traveling motor connected with a second wheel; and a control system which controls the first traveling motor and the second traveling motor. The control system estimates a first friction coefficient between the first wheel and a road surface and a second friction coefficient between the second wheel and the road surface. At a vehicle start time with at least one of the first friction coefficient and the second friction coefficient being less than a first threshold and with a difference between the first friction coefficient and the second friction coefficient being more than a second threshold, if the first friction coefficient is smaller than the second friction coefficient, the control system raises power running torque of the second traveling motor, and then, raises a power running torque of the first traveling motor after an elapse of a first delay time preset based on the first friction coefficient.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a vehicle control device provided in a vehicle.

Background Art

[0002] Vehicles equipped with a plurality of driving motors as power sources have been developed (see Patent Documents 1 to 3). As such vehicles, vehicles equipped with a driving motor connected to the front wheels and a driving motor connected to the rear wheels, and vehicles in which one driving motor is connected to each wheel have been developed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, since the torque of the driving motor rises quickly, there is a risk that the slip amount of the wheels driven by the motor will increase when starting the vehicle on a low-μ road such as a snow-packed road surface or a frozen road surface. Thus, since greatly slipping the wheels at the time of starting the vehicle is a factor that makes the vehicle behavior unstable, it is required to suppress the slip of the wheels at the time of starting the vehicle.

[0005] An object of the present invention is to suppress the slip of wheels at the time of starting a vehicle.

Means for Solving the Problems

[0006] A vehicle control device according to an embodiment is a vehicle control device provided in a vehicle, and includes a first driving motor connected to a first wheel, a second driving motor connected to a second wheel, a processor and a memory that are communicably connected to each other, and a control system that controls the first driving motor and the second driving motor. The control system estimates a first friction coefficient between the first wheel and the road surface and a second friction coefficient between the second wheel and the road surface. When at least one of the first friction coefficient and the second friction coefficient is less than a first threshold value and the difference between the first friction coefficient and the second friction coefficient exceeds a second threshold value during vehicle start, if the first friction coefficient is smaller than the second friction coefficient, after increasing the driving torque of the second driving motor and after a first delay time set based on the first friction coefficient has elapsed, the driving torque of the first driving motor is increased. On the other hand, if the second friction coefficient is smaller than the first friction coefficient, after increasing the driving torque of the first driving motor and after a second delay time set based on the second friction coefficient has elapsed, the driving torque of the second driving motor is increased.

Advantages of the Invention

[0007] A vehicle control device according to an embodiment, when at least one of a first friction coefficient and a second friction coefficient is less than a first threshold value and the difference between the first friction coefficient and the second friction coefficient exceeds a second threshold value during vehicle start, if the first friction coefficient is smaller than the second friction coefficient, after increasing the driving torque of the second driving motor and after a first delay time set based on the first friction coefficient has elapsed, the driving torque of the first driving motor is increased. Thereby, slip of the wheels during vehicle start can be suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail based on the drawings. In the following description, the same or substantially the same configurations and elements are denoted by the same reference numerals, and repeated descriptions thereof are omitted.

[0010] [Vehicle Configuration] FIG. 1 is a diagram showing a configuration example of a vehicle 11 provided with a vehicle control device 10 according to an embodiment of the present invention. As shown in FIG. 1, the vehicle 11 is provided with a front drive unit 13 that drives the front wheels 12L and 12R, and a rear drive unit 15 that drives the rear wheels 14L and 14R. The front drive unit 13 incorporates a front motor 16 and a front differential 17. Further, the rear drive unit 15 incorporates a rear motor 18 and a rear differential 19. As will be described later, a front motor (first traveling motor) 16 is connected to the front wheels (first wheels) 12L and 12R, and a rear motor (second traveling motor) 18 is connected to the rear wheels (second wheels) 14L and 14R.

[0011] FIG. 2 is a diagram showing an example of the front drive unit 13, the rear drive unit 15, and the control system 20. As shown in FIG. 2, the front drive unit 13 has a front motor 16 and a front differential 17. A drive gear 21 is connected to the rotor 16r of the front motor 16, and a driven gear 22 fixed to the front differential 17 meshes with the drive gear 21. Further, the front wheels 12L and 12R are connected to an axle 23 extending from the front differential 17. Similarly, the rear drive unit 15 has a rear motor 18 and a rear differential 19. A drive gear 24 is connected to the rotor 18r of the rear motor 18, and a driven gear 25 fixed to the rear differential 19 meshes with the drive gear 24. Further, the rear wheels 14L and 14R are connected to an axle 26 extending from the rear differential 19.

[0012] An inverter 30 is connected to the stator 16s of the front motor 16, and a battery pack 31 is connected to the inverter 30. Similarly, an inverter 32 is connected to the stator 18s of the rear motor 18, and the battery pack 31 is connected to the inverter 32. The battery pack 31 is provided with a battery module 33 composed of a plurality of battery cells, and a battery control unit 34 for monitoring the charge and discharge of the battery module 33 is provided. Further, the battery pack 31 is provided with a battery sensor 35 for detecting the charge and discharge current, terminal voltage, etc. The battery control unit 34 has a function of calculating the state of charge (SOC) of the battery module 33 based on the charge and discharge current, terminal voltage, etc. detected by the battery sensor 35. Note that the SOC of the battery module 33 is a ratio indicating the remaining electric quantity stored in the battery module 33, and is the ratio of the stored electric quantity to the full charge capacity of the battery module 33.

[0013] To control the front motor 16 via the inverter 30, a front motor control unit 40 is connected to the inverter 30. The front motor control unit 40 controls the energization state of the stator 16s by controlling the inverter 30 composed of a plurality of switching elements, etc., to control the motor torque (driving torque, regenerative torque) of the front motor 16. When controlling the front motor 16 to the driving state, power is supplied from the battery module 33 to the stator 16s via the inverter 30. On the other hand, when controlling the front motor 16 to the power generation state, power is supplied from the stator 16s to the battery module 33 via the inverter 30.

[0014] Similarly, in order to control the rear motor 18 via the inverter 32, a rear motor control unit 41 is connected to the inverter 32. The rear motor control unit 41 controls the energization state of the stator 18s by controlling the inverter 32 composed of a plurality of switching elements and the like, thereby controlling the motor torque (power running torque, regenerative torque) of the rear motor 18. When controlling the rear motor 18 in the power running state, power is supplied from the battery module 33 to the stator 18s via the inverter 32. On the other hand, when controlling the rear motor 18 in the power generation state, power is supplied from the stator 18s to the battery module 33 via the inverter 32.

[0015] In addition, left and right camera modules 43L and 43R for imaging the road surface with which the front and rear wheels 12L, 12R, 14L, and 14R come into contact are provided on the side mirrors 42L and 42R of the vehicle 11. A camera control unit 44 is connected to the camera modules 43L and 43R. The camera control unit 44 has a function of imaging the road surface with which the front and rear wheels 12L, 12R, 14L, and 14R come into contact during parking and performing image analysis of the captured image data to determine the road surface condition. Further, the camera control unit 44 has a function of estimating the friction coefficient between the front wheels 12L and 12R and the road surface with which they come into contact, and estimating the friction coefficient between the rear wheels 14L and 14R and the road surface with which they come into contact based on the road surface condition (dry road surface, wet road surface, snow-packed road surface, frozen road surface, etc.) of each road surface.

[0016] The vehicle 11 is provided with a brake device 45 for braking the front wheels 12L, 12R and the rear wheels 14L, 14R. The brake device 45 includes a master cylinder 47 that outputs brake hydraulic pressure in conjunction with the brake pedal 46, and a caliper 49 that brakes the disc rotors 48 of the front and rear wheels 12L, 12R, 14L, and 14R. A brake actuator 50 for controlling the brake hydraulic pressure supplied to each caliper 49 is provided between the master cylinder 47 and the caliper 49. The brake actuator 50 is composed of an electric pump, an accumulator, an electromagnetic valve, etc. (not shown).

[0017] In addition, a brake control unit 51 is connected to the brake actuator 50. The brake control unit 51 determines the locking tendency of the front and rear wheels 12L, 12R, 14L, 14R during braking and the slipping tendency of the front and rear wheels 12L, 12R, 14L, 14R during acceleration. When it is determined that the front and rear wheels 12L, 12R, 14L, 14R have a locking tendency, the brake control unit 51 reduces the braking force of the front and rear wheels 12L, 12R, 14L, 14R to eliminate the locking tendency. On the other hand, when it is determined that the front and rear wheels 12L, 12R, 14L, 14R have a slipping tendency, the brake control unit 51 increases the braking force of the front and rear wheels 12L, 12R, 14L, 14R to eliminate the slipping tendency. That is, the brake control unit 51 controls the brake actuator 50 to adjust the brake hydraulic pressure, thereby adjusting the braking force of the front and rear wheels 12L, 12R, 14L, 14R to eliminate the locking tendency and slipping tendency of the front and rear wheels 12L, 12R, 14L, 14R.

[0018] [Control System] In the vehicle control device 10, a control system 20 composed of a plurality of electronic control units is provided to control the front drive unit 13, the rear drive unit 15, etc. As the electronic control units constituting the control system 20, the battery control unit 34, the front motor control unit 40, the rear motor control unit 41, the camera control unit 44, and the brake control unit 51 described above are provided. In addition, a vehicle control unit 52 that outputs control signals to these control units 34, 40, 41, 44, 51 is provided. These control units 34, 40, 41, 44, 51, 52 are communicably connected to each other via an in-vehicle network 53 such as CAN or LIN. The vehicle control unit 52 sets operation targets for the front motor 16, the rear motor 18, etc. based on input information from various control units 34, 40, 41, 44, 51 and various sensors described later. Then, control signals corresponding to the operation targets of the front motor 16, the rear motor 18, etc. are generated, and these control signals are output to the various control units 34, 40, 41, 44, 51.

[0019] As sensors connected to the vehicle control unit 52, there are an accelerator sensor 60 that detects the operation status of the accelerator pedal, a brake sensor 61 that detects the operation status of the brake pedal 46, a wheel speed sensor 62 that detects the rotational speed of the left front wheel 12L, a wheel speed sensor 63 that detects the rotational speed of the right front wheel 12R, a wheel speed sensor 64 that detects the rotational speed of the left rear wheel 14L, and a wheel speed sensor 65 that detects the rotational speed of the right rear wheel 14R. Also, as a sensor connected to the front motor control unit 40, there is a motor rotation sensor 66 such as a resolver that detects the rotational speed of the front motor 16, and as a sensor connected to the rear motor control unit 41, there is a motor rotation sensor 67 such as a resolver that detects the rotational speed of the rear motor 18. Further, a start switch 68 operated by the driver when starting the control system 20 is connected to the vehicle control unit 52.

[0020] Figure 3 is a diagram briefly showing the basic structures of the respective control units 34, 40, 41, 44, 51, 52. As shown in Figure 3, the respective control units 34, 40, 41, 44, 51, 52 have a microcontroller 72 in which a processor 70, a memory 71, etc. are incorporated. A predetermined program is stored in the memory 71, and the program instruction set is executed by the processor 70. The processor 70 and the memory 71 are connected to be communicable with each other. In the illustrated example, one processor 70 and one memory 71 are incorporated in the microcontroller 72, but it is not limited to this, and a plurality of processors 70 may be incorporated in the microcontroller 72, or a plurality of memories 71 may be incorporated in the microcontroller 72.

[0021] In addition, each of the control units 34, 40, 41, 44, 51, 52 is provided with an input conversion circuit 73, a drive circuit 74, a communication circuit 75, an external memory 76, a power supply circuit 77, etc. The input conversion circuit 73 converts a signal input from various sensors into a signal that can be input to the microcontroller 72. The drive circuit 74 generates a drive signal for an actuator such as the front motor 16 or the rear motor 18 described above based on a signal output from the microcontroller 72. The communication circuit 75 converts a signal output from the microcontroller 72 into a communication signal directed to another control unit. Also, the communication circuit 75 converts a communication signal received from another control unit into a signal that can be input to the microcontroller 72. Furthermore, the power supply circuit 77 supplies a stable power supply voltage to the microcontroller 72, the input conversion circuit 73, the drive circuit 74, the communication circuit 75, the external memory 76, etc. In addition, data and the like that should be retained even when power is off are stored in the external memory 76 such as a non-volatile memory.

[0022] [Required driving force] FIG. 4 is a diagram showing an example of a driving force map indicating the required driving force. As shown in FIG. 4, characteristic lines L1 to L4 indicating the required driving force are set in the driving force map for each accelerator opening Acp. That is, when the accelerator opening Acp is 0%, the vehicle control unit 52 sets the required driving force for the vehicle 11 along the characteristic line L1, and when the accelerator opening Acp is 25%, the vehicle control unit 52 sets the required driving force for the vehicle 11 along the characteristic line L2. Also, when the accelerator opening Acp is 50%, the vehicle control unit 52 sets the required driving force for the vehicle 11 along the characteristic line L3, and when the accelerator opening Acp is 100%, the vehicle control unit 52 sets the required driving force for the vehicle 11 along the characteristic line L4.

[0023] For example, when the vehicle speed is "0" and the accelerator pedal is depressed so that the accelerator opening Acp is "25%", the vehicle control unit 52 sets "Fa" as the required driving force. Also, when the vehicle is stopped and the accelerator pedal is depressed so that the accelerator opening Acp is "50%", the vehicle control unit 52 sets "Fb" as the required driving force. Then, the vehicle control unit 52 sets the target motor torque T1 of the front motor 16 and the rear motor 18 so that the required driving forces "Fa" and "Fb" can be obtained. Although four characteristic lines L1 to L4 are set in the driving force map shown in FIG. 4 from the viewpoint of facilitating explanation, it goes without saying that the driving force map is not limited to this, and a driving force map with five or more characteristic lines may be used.

[0024] [Vehicle start on a low-μ road] By the way, when starting the vehicle on a low friction coefficient road surface such as a frozen road surface (hereinafter referred to as a low-μ road), if the motor torque of the front motor 16 or the rear motor 18 is rapidly increased, there is a risk of greatly slipping the front and rear wheels 12L, 12R, 14L, 14R and making the vehicle behavior unstable. Therefore, the control system 20 that constitutes the vehicle control device 10 executes starting torque suppression control that adjusts the rise of the motor torque according to the road surface conditions in order to suppress the slip of the front and rear wheels 12L, 12R, 14L, 14R and stabilize the vehicle behavior.

[0025] Hereinafter, the starting torque suppression control and the suppression condition setting control preceding it will be described. FIG. 5 is a flowchart showing an example of the execution procedure of the suppression condition setting control, and FIG. 6 is a flowchart showing an example of the execution procedure of the starting torque suppression control. In FIGS. 5 and 6, the front motor 16 and the rear motor 18 are described as driving motors, the front wheels 12L, 12R and the rear wheels 14L, 14R are described as wheels, the high friction coefficient side is described as the high μ side, and the low friction coefficient side is described as the low μ side. Note that the high friction coefficient side and the low friction coefficient side mean the relatively high friction coefficient side and the relatively low friction coefficient side. Each step shown in the flowcharts of FIGS. 5 and 6 shows a process executed by one or a plurality of processors 70 constituting the control system 20. Also, the suppression condition setting control shown in FIG. 5 and the starting torque suppression control shown in FIG. 6 are controls executed by the control system 20 at predetermined intervals after the start switch 68 is operated by the driver and the control system 20 including the vehicle control unit 52 and the like is activated.

[0026] <Suppression Condition Setting Control (Flowchart)> First, the suppression condition setting control preceding the starting torque suppression control will be described. As shown in FIG. 5, in step S10, in order to determine whether the vehicle 11 is stopped, it is determined whether the vehicle speed is lower than a predetermined threshold value V1. In step S10, if it is determined that the vehicle speed is lower than the threshold value V1, that is, if it is determined that the vehicle 11 is stopped, the process proceeds to step S11, and the friction coefficients Fμ, Rμ between the wheels and the road surface are estimated. That is, in step S11, image analysis of the imaging data obtained by the camera modules 43L, 43R is executed to determine the road surface condition, and the friction coefficients Fμ, Rμ between the wheels and the road surface are estimated from the determined road surface condition (dry road surface, wet road surface, snow-packed road surface, frozen road surface, etc.). Note that the friction coefficient (first friction coefficient) Fμ is the average value of the friction coefficients between the left and right front wheels 12L, 12R and the road surface Sf (see FIG. 1) in contact therewith, and the friction coefficient (second friction coefficient) Rμ is the average value of the friction coefficients between the left and right rear wheels 14L, 14R and the road surface Sr (see FIG. 1) in contact therewith.

[0027] Subsequently, in step S12, it is determined whether the friction coefficient Fμ is less than a predetermined threshold value (first threshold value) μ1. In step S12, if it is determined that the friction coefficient Fμ is equal to or greater than the threshold value μ1, that is, if it is determined that the front wheels 12L and 12R are in contact with a non-slip road surface such as a dry road surface, the process proceeds to step S13. In step S13, it is determined whether the friction coefficient Rμ is less than the threshold value μ1. In step S13, if it is determined that the friction coefficient Rμ is equal to or greater than the threshold value μ1, that is, if it is determined that the rear wheels 14L and 14R are in contact with a non-slip road surface such as a dry road surface, the process proceeds to step S14. That is, if it is determined that both the front wheels 12L and 12R and the rear wheels 14L and 14R are in contact with a non-slip road surface, since it is not necessary to execute the starting torque suppression control described later, the process proceeds to step S14 and the low μ road start flag is released (Fs = 0).

[0028] On the other hand, in step S12, if it is determined that the friction coefficient Fμ is less than the threshold value μ1, or in step S13, if it is determined that the friction coefficient Rμ is less than the threshold value μ1, the process proceeds to step S15. That is, if it is determined that at least one of the front wheels 12L and 12R and the rear wheels 14L and 14R is in contact with a slippery road surface, the process proceeds to step S15, and it is determined whether the absolute value of the difference between the friction coefficient Fμ and the friction coefficient Rμ exceeds a predetermined threshold value (second threshold value) Xμ. In step S15, if it is determined that the absolute value of the difference between the friction coefficient Fμ and the friction coefficient Rμ exceeds the threshold value Xμ, the process proceeds to step S16. In step S16, a smoothing coefficient ks for the driving motor on the high friction coefficient side (hereinafter referred to as the high μ side) is set, and in the subsequent step S17, a delay time Td for the driving motor on the low friction coefficient side (hereinafter referred to as the low μ side) is set.

[0029] As described above, when at least one of the friction coefficients Fμ and Rμ is lower than the threshold value μ1 and the difference between the friction coefficients Fμ and Rμ exceeds the threshold value Xμ, the process proceeds to step S16, where the smoothing coefficient ks for the driving motor on the high-μ side is set, and then to step S17, where the delay time Td for the driving motor on the low-μ side is set. That is, when the friction coefficient Fμ is smaller than the friction coefficient Rμ and the front wheels 12L and 12R are prone to slipping, the smoothing coefficient ks for the rear motor 18 on the high-μ side is set, and the delay time Td for the front motor 16 on the low-μ side is set. On the other hand, when the friction coefficient Rμ is smaller than the friction coefficient Fμ and the rear wheels 14L and 14R are prone to slipping, the smoothing coefficient ks for the front motor 16 on the high-μ side is set, and the delay time Td for the rear motor 18 on the low-μ side is set. Thus, when the smoothing coefficient ks and the delay time Td are set in steps S16 and S17, the process proceeds to step S18, where the low-μ road start flag Fs is set (Fs = 1).

[0030] Also, in step S15, when it is determined that the absolute value of the difference between the friction coefficient Fμ and the friction coefficient Rμ is less than or equal to the threshold value Xμ, the process proceeds to step S19. In step S19, the smoothing coefficient ks for both driving motors is set. That is, the smoothing coefficient ks for the front motor 16 is set, and at the same time, the smoothing coefficient ks for the rear motor 18 is set. Thus, when the smoothing coefficient ks is set in step S19, the process proceeds to step S18, where the low-μ road start flag Fs is set (Fs = 1).

[0031] Here, FIG. 7 is a diagram showing an example of the smoothing coefficient ks and an example of the control of the motor torque. As shown in FIG. 7, the smoothing coefficient ks is set to be smaller as the friction coefficient becomes smaller. Also, regarding the motor torque output from the driving motors such as the front motor 16 and the rear motor 18, the motor torque is controlled to be smaller as the smoothing coefficient ks is set to be smaller. For example, when the accelerator pedal is operated along the solid line Acp1 and the aforementioned target motor torque T1 is set as the target motor torque, the motor torque of the driving motor is controlled toward the target motor torque T1. At this time, when "α" is set as the smoothing coefficient ks, the motor torque Ta is set by multiplying the target motor torque T1 by the smoothing coefficient α, and the driving motor is controlled toward the motor torque Ta subjected to the smoothing process. Also, when "β" is set as the smoothing coefficient ks, the motor torque Tb is set by multiplying the target motor torque T1 by the smoothing coefficient β, and the driving motor is controlled toward the motor torque Tb subjected to the smoothing process.

[0032] In this way, by performing the smoothing process on the motor torque of the driving motor, the power running torque of the driving motor is controlled to be smaller than the target motor torque (target torque) T1 based on the required driving force. Also, as described above, the smoothing coefficient ks is set to be smaller as the friction coefficient becomes smaller. As a result, the power running torque of the driving motor is controlled to be smaller as the friction coefficient becomes smaller. Note that the method of controlling the power running torque of the driving motor to be smaller than the target motor torque T1 is not limited to the control method using the smoothing coefficient. For example, the upper limit torque of the driving motor may be set based on the friction coefficient, or the torque increase rate of the driving motor may be limited based on the friction coefficient.

[0033] FIG. 8 is a diagram showing an example of the delay time Td and an example of control of the motor torque. As shown in FIG. 8, the delay time Td is set to be longer as the friction coefficient becomes smaller. Then, with respect to the motor torque output from the traveling motors such as the front motor 16 and the rear motor 18, the increase starts after the elapse of the delay time Td from the depression of the accelerator pedal. For example, when the accelerator pedal is operated along the solid line Acp1 and the aforementioned target motor torque T1 is set as the target motor torque, the motor torque of the traveling motor is controlled toward the target motor torque T1. Here, when the delay time Td is set, as shown by the dashed line Tc, the motor torque is held at "0" until the delay time Td elapses from the start of the operation of the accelerator pedal, and the motor torque is pulled up after the delay time Td has elapsed.

[0034] <Acceleration Torque Suppression Control (Flowchart)> Next, the acceleration torque suppression control will be described. As shown in FIG. 6, in step S20, in order to determine whether or not the vehicle 11 is stopped, it is determined whether or not the vehicle speed is lower than a predetermined threshold value V1. In step S20, if it is determined that the vehicle speed is lower than the threshold value V1, that is, if it is determined that the vehicle 11 is stopped, the process proceeds to step S21, and it is determined whether or not the low-μ road start flag Fs is set to "1". In step S21, if it is determined that the low-μ road start flag Fs is set to "1", the process proceeds to step S23, and it is determined whether or not the start condition of the vehicle 11 is satisfied. Here, as the start condition of the vehicle 11, the accelerator pedal may be depressed or the depression of the brake pedal 46 may be released.

[0035] In step S23, when it is determined that the starting condition of the vehicle 11 is satisfied, the process proceeds to step S24, and the target motor torque T1 is set based on the required driving force described above. This target motor torque T1 is the target motor torque set for the front motor 16 and the rear motor 18 so that the required driving force set using the driving force map in FIG. 4 can be obtained. Then, when the target motor torque T1 is set for each driving motor, the process proceeds to step S25, and the corrected motor torque T2 is set based on the delay time Td and the smoothing coefficient ks described above. This corrected motor torque T2 is the motor torque that is suppressed and output based on the smoothing coefficient ks and is the motor torque that is output with a delay based on the delay time Td, as shown in FIGS. 7 and 8. Also, when the corrected motor torque T2 is set for each driving motor, the process proceeds to step S26, and the final motor torque T3 is set based on the brake control. This final motor torque T3 is the motor torque that is corrected so as not to affect the braking force control when the braking force control for suppressing wheel slip or the like is executed by the brake device 45 described above.

[0036] In this way, when the final motor torque T3 is set for each driving motor, the process proceeds to step S27, and the front motor 16 is controlled based on the final motor torque T3 for the front motor, and the rear motor 18 is controlled based on the final motor torque T3 for the rear motor. That is, when starting the vehicle 11 on a low-μ road such as an icy road surface, the delay time Td and the smoothing coefficient ks are set based on the friction coefficients Fμ, Rμ, and the motor torques of the front motor 16 and the rear motor 18 are suppressed by this delay time Td and the smoothing coefficient ks. Thereby, excessive slip of the front and rear wheels 12L, 12R, 14L, 14R can be suppressed, and the behavior of the vehicle 11 starting on a low-μ road can be stabilized.

[0037] Subsequently, in step S28, it is determined whether the vehicle speed after starting exceeds a predetermined threshold value V2. In step S28, if it is determined that the vehicle speed is equal to or lower than the threshold value V2, the process proceeds to step S29, and it is determined whether the elapsed time after starting exceeds a predetermined torque suppression time. In step S29, if it is determined that the elapsed time after starting is equal to or shorter than the torque suppression time, the process returns to step S24, and the torque suppression control of each driving motor is continued. That is, when the vehicle speed after starting is equal to or lower than the threshold value V2 and the elapsed time after starting is equal to or shorter than the torque suppression time, the process returns to step S24, and the torque suppression control of each driving motor is continued.

[0038] On the other hand, in step S28, if it is determined that the vehicle speed after starting exceeds the threshold value V2, or in step S29, if it is determined that the elapsed time after starting exceeds the torque suppression time, the process proceeds to step S30, the low μ road start flag is reset (Fs = 0), the process proceeds to step S31, and normal control of the driving motor is executed. Note that the normal control of the driving motor is control for setting the target motor torque based on the accelerator opening and the vehicle speed without using the aforementioned delay time Td and the smoothing coefficient ks.

[0039] [Starting Torque Suppression Control (Timing Chart 1)] The execution status of the above-described starting torque suppression control will be described with reference to a timing chart. FIG. 9 is a timing chart showing an example of the execution status of the starting torque suppression control, and FIG. 10 is a diagram showing a vehicle 11 starting by the starting torque suppression control. Note that the times t3 and t4 shown in FIG. 9 correspond to the times t3 and t4 shown in FIG. 10. In addition, the situations shown in FIGS. 9 and 10 are situations in which the vehicle 11 is started by depressing the accelerator pedal from a stopped state in which the front wheels 12L and 12R are stopped on an icy road surface or the like and the rear wheels 14L and 14R are stopped on a snow-packed road surface or the like.

[0040] As shown at time t1 in FIG. 9, when the vehicle speed falls below the threshold value V1 in preparation for stopping (reference sign a1), the friction coefficient Fμ between the front wheels 12L and 12R and the road surface in contact therewith is estimated, and the friction coefficient Rμ between the rear wheels 14L and 14R and the road surface in contact therewith is estimated. Then, as shown at time t2, when the friction coefficients Fμ and Rμ fall below the threshold value μ1 and the difference (|Fμ - Rμ|) between the friction coefficients Fμ and Rμ exceeds the threshold value Xμ and this situation continues for a predetermined time (reference signs b1, c1, d1), the aforementioned delay time Td and the smoothing coefficient ks are set, and the low μ road start flag Fs, which is an execution condition for torque suppression control, is set (reference sign e1). In the illustrated example, since the friction coefficient Fμ is smaller than the friction coefficient Rμ, the delay time Td for the front motor 16 on the low μ side is set, and the smoothing coefficient ks for the rear motor 18 on the high μ side is set.

[0041] As shown at time t3, when the accelerator pedal is depressed by the driver (reference sign f1), the target motor torques T1 of the front motor 16 and the rear motor 18 increase according to the accelerator opening (reference signs g1, h1). Here, since the delay time Td is set for the front motor 16, the motor torque Tf of the front motor 16 is controlled to "0" over the delay time Td without following the target motor torque T1 (reference sign i1). Further, the smoothing coefficient ks is set for the rear motor 18 based on the friction coefficient Rμ, and the motor torque Tr of the rear motor 18 for which smoothing processing is performed is controlled to be smaller than and gentler than the target motor torque T1 (reference sign j1).

[0042] Also, as shown at time t4, when the delay time Td elapses since the accelerator pedal was depressed, the motor torque Tf of the front motor 16 is controlled toward the target motor torque T1 (reference sign i2). Next, as shown at time t5, when the vehicle speed reaches a predetermined threshold value V2 (reference sign a2), the low μ road start flag is canceled in order to terminate the torque suppression control using the delay time Td and the smoothing coefficient ks (reference sign e2). Then, the motor torque Tr of the rear motor 18 is controlled toward the target motor torque T1 (reference sign j2).

[0043] As described above, when the vehicle starts moving and the friction coefficients Fμ and Rμ are less than the threshold value μ1 and the difference (|Fμ - Rμ|) of the friction coefficients Fμ and Rμ is greater than the threshold value Xμ, if the friction coefficient Fμ is smaller than the friction coefficient Rμ, the power running torque of the rear motor 18 is increased, and after the delay time (first delay time) Td based on the friction coefficient (first friction coefficient) Fμ has elapsed, the power running torque of the front motor 16 is increased. That is, after starting to increase the power running torque of the rear motor 18, the power running torque of the front motor 16 starts to increase after the delay time Td has elapsed. That is, as shown as time t3 in FIG. 10, when the friction coefficient Fμ is smaller than the friction coefficient Rμ, that is, when the front wheels 12L and 12R are stopped on a road surface that is more slippery than the rear wheels 14L and 14R, the power running torque of the rear motor 18 is increased prior to that of the front motor 16.

[0044] In this way, while applying the driving force Fr to the rear wheels 14L and 14R in contact with the snow-packed road surface that is less slippery than the frozen road surface, the driving force for the front wheels 12L and 12R in contact with the frozen road surface that is more slippery than the snow-packed road surface is controlled to zero. As a result, while applying the driving force Fr to the rear wheels 14L and 14R on the high μ side to start the vehicle 11, the front wheels 12L and 12R on the low μ side can be rotated in conjunction with the vehicle speed so as not to slip. When the vehicle 11 is started in this way, as shown as time t4 in FIG. 10, after the front wheels 12L and 12R rotate over the delay time Td, the power running torque of the front motor 16 is increased, whereby the driving force Ff is applied to the rotating front wheels 12L and 12R. Thereby, slipping of the front wheels 12L and 12R in contact with a frozen road surface or the like can be suppressed, and the vehicle behavior at the start can be stabilized.

[0045] As described above, when the vehicle starts with the front and rear wheels 12L, 12R, 14L, 14R contacting a low-μ road such as an icy road surface, if the difference between the front and rear friction coefficients Fμ and Rμ is large, while applying a driving force Fr to the rear wheels 14L, 14R on the high-μ side, the driving force for the front wheels 12L, 12R on the low-μ side is controlled to zero over a delay time Td. Then, after the front wheels 12L, 12R rotate for the delay time Td, by increasing the power running torque of the front motor 16, a driving force Ff is applied to the rotating front wheels 12L, 12R. In this way, by rotating the front wheels 12L, 12R for the delay time Td, it is possible to suppress the slip of the front wheels 12L, 12R, and this delay time Td can be calculated based on the friction coefficient and the like.

[0046] First, the allowable slip amount of the wheels driven by the driving motor is set as a target slip amount SL [km / h]. Regarding this target slip amount SL, it is possible to convert it into a torque overshoot amount Tos [Nm] of the driving motor by using the gear ratio of the drive system and the like. This torque overshoot amount Tos is the motor torque Tma [Nm] allowed for the driving motor from the perspective of restricting the slip amount of the wheels to be below the target slip amount SL. That is, as shown in the following formula (1), by subtracting the dynamic frictional force Ffri [Nm] acting on the wheels from the torque overshoot amount Tos and controlling the motor torque Tma of the driving motor so as not to exceed this subtraction value, it is possible to restrict the slip amount of the wheels to be below the target slip amount SL. Note that the dynamic frictional force Ffri can be calculated using the friction coefficient between the corresponding wheel and the road surface. As described above, when the motor torque Tma of the driving motor to be restricted is obtained, as shown in the following formula (2), by dividing the motor torque Tma by the torque increase rate Rm [Nm / msec] of the driving motor, the delay time Td [msec] is calculated. By executing zero torque control over the delay time Td calculated in this way, it is possible to increase the rotational speed of the corresponding wheels so as not to exceed the target slip amount SL. Tma [Nm] ≤ Tos [Nm] - Ffri [Nm] ··· Equation (1) Td [msec] = Tma [Nm] / Rm [Nm / msec] ··· Equation (2)

[0047] In the examples shown in FIGS. 9 and 10, the case where the friction coefficient Fμ is smaller than the friction coefficient Rμ is shown, but it is not limited to this. That is, in the examples shown in FIGS. 9 and 10, when the friction coefficient Rμ is smaller than the friction coefficient Fμ, that is, when the rear wheels 14L and 14R are stopped on a road surface that is more slippery than the front wheels 12L and 12R, a delay time (second delay time) Td based on the friction coefficient (second friction coefficient) Rμ is set for the rear motor 18 on the low μ side. And when starting the vehicle, after increasing the driving torque of the front motor 16, after the delay time Td based on the friction coefficient Rμ has elapsed, the driving torque of the rear motor 18 is increased. That is, after starting to increase the driving torque of the front motor 16, after the delay time Td has elapsed, the driving torque of the rear motor 18 starts to increase. Also, in the above description, the smoothing process is performed on the driving motor on the high μ side, but it is not limited to this, and the vehicle 11 may be started without performing the smoothing process on the driving motor on the high μ side.

[0048] [Acceleration Torque Suppression Control (Timing Chart 2)] The timing chart shown in FIG. 9 above shows a situation where the difference (|Fμ - Rμ|) between the friction coefficients Fμ and Rμ exceeds the threshold value Xμ. In the following explanation, a situation where the friction coefficients Fμ and Rμ are below the threshold value μ1 and the difference (|Fμ - Rμ|) between the friction coefficients Fμ and Rμ is below the threshold value Xμ will be described. Here, FIG. 11 is a timing chart showing an example of the execution status of the acceleration torque suppression control.

[0049] As shown at time t1 in FIG. 11, when the vehicle speed drops below the threshold value V1 in preparation for stopping (reference sign a1), the friction coefficient Fμ between the front wheels 12L and 12R and the road surface in contact therewith is estimated, and the friction coefficient Rμ between the rear wheels 14L and 14R and the road surface in contact therewith is estimated. Then, as shown at time t2, when the friction coefficients Fμ and Rμ drop below the threshold value μ1 and the difference (|Fμ - Rμ|) between the friction coefficients Fμ and Rμ drops below the threshold value Xμ and this situation continues for a predetermined time (reference signs b1, c1, d1), a softening coefficient ks is set for both driving motors, and a low μ road start flag Fs, which is a condition for executing torque suppression control, is set (reference sign e1). That is, the softening coefficient ks for the front motor 16 is set, and the softening coefficient ks for the rear motor 18 is set.

[0050] As shown at time t3, when the accelerator pedal is depressed by the driver (reference sign f1), the target motor torques T1 of the front motor 16 and the rear motor 18 increase according to the accelerator opening (reference signs g1, h1). Here, the softening coefficient ks is set for the front motor 16 based on the friction coefficient Fμ, and the motor torque Tf of the front motor 16 for which the softening process is performed is made smaller than the target motor torque T1 and is gently controlled (reference sign i1). Similarly, the softening coefficient ks is set for the rear motor 18 based on the friction coefficient Rμ, and the motor torque Tr of the rear motor 18 for which the softening process is performed is made smaller than the target motor torque T1 and is gently controlled (reference sign j1).

[0051] Next, as shown at time t4, when the vehicle speed reaches a predetermined threshold value V2 (reference sign a2), the low μ road start flag is released in order to end the torque suppression control using the softening coefficient ks (reference sign e2). Then, the motor torque Tf of the front motor 16 is controlled toward the target motor torque T1 (reference sign i2), and the motor torque Tr of the rear motor 18 is controlled toward the target motor torque T1 (reference sign j2).

[0052] As described above, when starting the vehicle where the friction coefficients Fμ and Rμ are below the threshold value μ1 and the difference in the friction coefficients Fμ and Rμ (|Fμ - Rμ|) is below the threshold value Xμ, since the friction coefficients Fμ and Rμ are approaching each other, smoothing processing is performed on both motor torques Tf and Tr. As a result, appropriate driving forces can be applied to the front and rear wheels 12L, 12R, 14L, and 14R, so that the starting performance of the vehicle 11 can be improved. Moreover, the motor torque Tf of the front motor 16 is controlled using a smoothing coefficient ks based on the friction coefficient Fμ, and the motor torque Tr of the rear motor 18 is controlled using a smoothing coefficient ks based on the friction coefficient Rμ. Thereby, since the motor torques Tf and Tr can be appropriately controlled according to the road surface conditions, the starting performance of the vehicle 11 can be improved and the vehicle behavior can be stabilized.

[0053] [Other Embodiments] <Vehicle Configuration> In the above description, one front motor 16 is connected to the left and right front wheels 12L and 12R, and one rear motor 18 is connected to the left and right rear wheels 14L and 14R. However, the present invention is not limited to this, and one driving motor may be connected to each of the wheels 12L, 12R, 14L, and 14R. Here, FIG. 12 is a diagram showing a configuration example of a vehicle 81 provided with a vehicle control device 80 according to another embodiment of the present invention. In FIG. 12, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

[0054] As shown in FIG. 12, the vehicle 81 includes a left front motor 84 connected to the left front wheel 82L, a right front motor 85 connected to the right front wheel 82R, a left rear motor 86 connected to the left rear wheel 83L, and a right rear motor 87 connected to the right rear wheel 83R. An inverter 90 is connected to the stator 84s of the left front motor 84, an inverter 91 is connected to the stator 85s of the right front motor 85, an inverter 92 is connected to the stator 86s of the left rear motor 86, and an inverter 93 is connected to the stator 87s of the right rear motor 87. Further, a battery pack 31 is connected to each of the inverters 90 to 93.

[0055] To control the left front motor 84 via the inverter 90, a left front motor control unit 94 is connected to the inverter 90. To control the right front motor 85 via the inverter 91, a right front motor control unit 95 is connected to the inverter 91. Also, to control the left rear motor 86 via the inverter 92, a left rear motor control unit 96 is connected to the inverter 92. To control the right rear motor 87 via the inverter 93, a right rear motor control unit 97 is connected to the inverter 93. The control system 98 is constituted by these motor control units 94 to 97 and the above-described respective control units 34, 44, 51, 52.

[0056] <Suppression Condition Setting Control (Flowchart)> Subsequently, the suppression condition setting control executed by the control system 98 constituting the vehicle control device 80 will be described. Here, FIGS. 13 to 15 are flowcharts showing an example of the execution procedure of the suppression condition setting control. In the flowcharts of FIGS. 13 to 15, the parts indicated by the symbols A and B are connected to each other. Also, in FIGS. 14 and 15, the left and right front motors 84, 85 and the left and right rear motors 86, 87 are described as traveling motors, and the left front wheel 82L, the right front wheel 82R, the left rear wheel 83L, and the right rear wheel 83R are described as wheels. Note that also in the vehicle control device 80, the starting torque suppression control is executed in accordance with the procedure shown in the flowchart of FIG. 6 described above.

[0057] As shown in FIG. 13, in step S40, in order to determine whether the vehicle 81 has stopped, it is determined whether the vehicle speed is lower than a predetermined threshold value V1. In step S40, if it is determined that the vehicle speed is lower than the threshold value V1, that is, if it is determined that the vehicle 81 has stopped, the process proceeds to step S41, and the friction coefficients FLμ, FRμ, RLμ, and RRμ between the wheels and the road surface are estimated. That is, in step S41, image analysis of the imaging data obtained by the camera modules 43L and 43R is executed to determine the road surface condition, and the friction coefficients FLμ, FRμ, RLμ, and RRμ between the wheels and the road surface are estimated from the determined road surface condition (dry road surface, wet road surface, snow-packed road surface, frozen road surface, etc.).

[0058] The friction coefficient FLμ is the friction coefficient between the left front wheel 82L and the road surface in contact therewith, and the friction coefficient FRμ is the friction coefficient between the right front wheel 82R and the road surface in contact therewith. The friction coefficient RLμ is the friction coefficient between the left rear wheel 83L and the road surface in contact therewith, and the friction coefficient RRμ is the friction coefficient between the right rear wheel 83R and the road surface in contact therewith.

[0059] Subsequently, in step S42, it is determined whether the friction coefficient FLμ is lower than a predetermined threshold value (first threshold value) μ1. In step S42, if it is determined that the friction coefficient FLμ is equal to or greater than the threshold value μ1, that is, if it is determined that the left front wheel 82L is in contact with a non-slip road surface such as a dry road surface, the process proceeds to step S43. In step S43, it is determined whether the friction coefficient FRμ is lower than the threshold value μ1. In step S43, if it is determined that the friction coefficient FRμ is equal to or greater than the threshold value μ1, that is, if it is determined that the right front wheel 82R is in contact with a non-slip road surface, the process proceeds to step S44.

[0060] Also, in step S44, it is determined whether the friction coefficient RLμ is less than the threshold value μ1. In step S44, if it is determined that the friction coefficient RLμ is equal to or greater than the threshold value μ1, that is, if it is determined that the left rear wheel 83L is in contact with a non - slippery road surface, the process proceeds to step S45. In step S45, it is determined whether the friction coefficient RRμ is less than the threshold value μ1. In step S45, if it is determined that the friction coefficient RRμ is equal to or greater than the threshold value μ1, that is, if it is determined that the right rear wheel 83R is in contact with a non - slippery road surface, the process proceeds to step S46. That is, when it is determined that all of the left front wheel 82L, the right front wheel 82R, the left rear wheel 83L, and the right rear wheel 83R are in contact with non - slippery road surfaces, since there is no need to execute the starting torque suppression control, the process proceeds to step S46 and the low - μ road start flag is released (Fs = 0).

[0061] On the other hand, in steps S42 - S4 5 if it is determined that any of the friction coefficients FLμ, FRμ, RLμ, RRμ is less than the threshold value μ1, the process proceeds to step S47. As shown in FIG. 14, in step S47, among the friction coefficients FLμ, FRμ, RLμ, RRμ, the highest friction coefficient is set as the reference friction coefficient XHμ. Also, among the respective wheels, the wheel corresponding to the reference friction coefficient XHμ is set as the reference wheel WH. In the subsequent step S48, among the friction coefficients FLμ, FRμ, RLμ, RRμ, the friction coefficients other than the reference friction coefficient XHμ are set as the friction coefficients XLμ1, XLμ2, XLμ3. Also, among the respective wheels, the wheels corresponding to the friction coefficients XLμ1, XLμ2, XLμ3 are set as the wheels WL1, WL2, WL3. Next, in step S49, as shown in the following equations (3) - (5), the differences Δμ1, Δμ2, Δμ3 between the reference friction coefficient XHμ and the friction coefficients XLμ1, XLμ2, XLμ3 are calculated. Δμ1 = XHμ - XLμ1 ·· Equation (3) Δμ2 = XHμ - XLμ2 ·· Equation (4) Δμ3 = XHμ - XLμ3 ·· Equation (5)

[0062] Subsequently, as shown in FIG. 15, the process proceeds to step S50, and the warm-up coefficient ksh of the driving motor for the reference wheel WH is set. In the subsequent step S51, it is determined whether or not the difference Δμ1 between the friction coefficients XHμ and XLμ1 exceeds a predetermined threshold value (second threshold value) Xμ. In step S51, if it is determined that the difference Δμ1 exceeds the threshold value Xμ, the process proceeds to step S52, and the delay time Td1 of the driving motor for the wheel WL1 is set. On the other hand, in step S51, if it is determined that the difference Δμ1 is equal to or less than the threshold value Xμ, the process proceeds to step S53, and the warm-up coefficient ks1 of the driving motor for the wheel WL1 is set.

[0063] In the subsequent step S54, it is determined whether or not the difference Δμ2 between the friction coefficients XHμ and XLμ2 exceeds the threshold value Xμ. In step S54, if it is determined that the difference Δμ2 exceeds the threshold value Xμ, the process proceeds to step S55, and the delay time Td2 of the driving motor for the wheel WL2 is set. On the other hand, in step S54, if it is determined that the difference Δμ2 is equal to or less than the threshold value Xμ, the process proceeds to step S56, and the warm-up coefficient ks2 of the driving motor for the wheel WL2 is set.

[0064] In the subsequent step S57, it is determined whether or not the difference Δμ3 between the friction coefficients XHμ and XLμ3 exceeds the threshold value Xμ. In step S57, if it is determined that the difference Δμ3 exceeds the threshold value Xμ, the process proceeds to step S58, and the delay time Td3 of the driving motor for the wheel WL3 is set. On the other hand, in step S57, if it is determined that the difference Δμ3 is equal to or less than the threshold value Xμ, the process proceeds to step S59, and the warm-up coefficient ks3 of the driving motor for the wheel WL3 is set.

[0065] In this way, after passing through each of steps S50 to S59 and setting the delay times Td1 to Td3 and the warm-up coefficients ksh, ks1 to ks3, the process proceeds to step S60, and the low μ road start flag Fs is set (Fs = 1). Regarding the delay times Td1 to Td3, as shown in the aforementioned figure 8It is set according to the setting procedure shown in the like, and for the smoothing coefficients ksh, ks1 to ks3, the above-mentioned figure 7 is set according to the setting procedure shown in the like.

[0066] As described so far, based on the friction coefficients FLμ, FRμ, RLμ, and RRμ estimated during parking, the delay times Td1 to Td3 of the driving motors for each wheel and the smoothing coefficients ksh, ks1 to ks3 are set. As a result, similar to the vehicle control device 10 described above, it is possible to suppress the slip of the wheels in contact with a frozen road surface or the like, and to stabilize the vehicle behavior at the time of starting. Moreover, in the present embodiment, since one driving motor is connected to each wheel, it is possible to more appropriately control the driving force of each wheel according to the road surface condition.

[0067] Here, FIG. 16 is a view showing a vehicle 81 starting by start torque suppression control. The situation shown in FIG. 16 is a situation where the right front wheel 82R, the left rear wheel 83L, and the right rear wheel 83R are stopped on a frozen road surface or the like, and the left front wheel 82L is stopped on a snow-packed road surface or the like, and the accelerator pedal is depressed to start the vehicle 81. That is, in the example shown in FIG. 16, the left front wheel 82L with the largest friction coefficient is set as the reference wheel WH, and the other right front wheel 82R, left rear wheel 83L, and right rear wheel 83R are set as the wheels WL1 to WL3. Further, a smoothing coefficient ksh is set for the left front motor 84 that drives the left front wheel 82L, and the other wheels are driven Right front motor 8 5 The delay times Td1 to Td3 are set for the left rear motor 86 and the right rear motor 87.

[0068] As shown in Fig. 16 immediately after starting, the right front wheel 82R, the left rear wheel 83L, and the right rear wheel 83R stop on an icy road surface or the like, and the left front wheel 82L stops on a snow-packed road surface or the like. Therefore, the driving torque Tfl of the left front motor 84 is increased ahead of the driving torques of the other driving motors. In this way, while applying the driving force Ffl to the left front wheel 82L in contact with the snow-packed road surface, which is less slippery than the icy road surface, the driving forces for the other wheels 82R, 83L, 83R in contact with the icy road surface, which is more slippery than the snow-packed road surface, are controlled to zero. As a result, while applying the driving force Ffl to the left front wheel 82L on the high-μ side to start the vehicle 81, the wheels 82R, 83L, 83R on the low-μ side can be rotated in conjunction with the vehicle speed so as not to slip. When the vehicle 81 is started in this way, as shown in Fig. 16 after a predetermined time has elapsed, after the wheels 82R, 83L, 83R rotate over the delay times Td1 to Td3, the driving torques Tfr, Trl, Trr of the other driving motors 85 to 87 are increased, whereby the driving forces Ffr, Frl, Frr are applied to the rotating wheels 82R, 83L, 83R. As a result, the slip of the wheels 82R, 83L, 83R in contact with the icy road surface or the like can be suppressed, and the vehicle behavior at the start can be stabilized.

[0069] In the vehicle control device 80, any one of the wheels 82L, 82R, 83L, 83R functions as a first wheel, and any one of the other wheels functions as a second wheel. Also, any one of the motors 84 to 87 functions as a first driving motor, and any one of the other motors functions as a second driving motor. Further, any one of the delay times Td1 to Td3 functions as a first delay time, and any one of the other delay times functions as a second delay time. Also, any one of the friction coefficients FLμ, FRμ, RLμ, RRμ functions as a first friction coefficient, and any one of the other friction coefficients functions as a second friction coefficient.

[0070] The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist thereof. In the above description, the control system 20 is constituted by a plurality of control units 34, 40, 41, 44, 51, 52, and the control system 98 is constituted by a plurality of control units 34, 44, 51, 52, 94 to 97, but the present invention is not limited thereto. For example, the control systems 20 and 98 may be constituted by one control unit. Note that the vehicles 11 and 81 are not limited to the illustrated electric vehicles, and may be fuel cell vehicles or series hybrid vehicles.

[0071] In the above description, the present invention is applied to all-wheel drive vehicles 11 and 81, but the present invention is not limited thereto, and the present invention may be applied to front-wheel drive or rear-wheel drive vehicles 11. That is, in a front-wheel drive vehicle, it is sufficient that the first driving motor is connected to the left front wheel (first wheel) and the second driving motor is connected to the right front wheel (second wheel). In this case, the softening coefficient ks and the delay time Td are set according to the friction coefficient of each road surface in contact with the left and right front wheels, and the above-described starting torque suppression control is executed. Similarly, in a rear-wheel drive vehicle, it is sufficient that the first driving motor is connected to the left rear wheel (first wheel) and the second driving motor is connected to the right rear wheel (second wheel). In this case, the softening coefficient ks and the delay time Td are set according to the friction coefficient of each road surface in contact with the left and right rear wheels, and the above-described starting torque suppression control is executed.

[0072] In the foregoing description, the image analysis of the imaging data obtained by the camera modules 43L and 43R is executed to determine the road surface condition, and the friction coefficient between the wheel and the road surface is estimated based on the determined road surface condition (dry road surface, wet road surface, snow-packed road surface, frozen road surface, etc.). However, it is not limited to this. For example, the friction coefficient between the wheel and the road surface may be estimated based on the regenerative torque of the driving motor immediately before stopping and the angular acceleration of the wheel connected to the driving motor. That is, at the timing when the wheel starts to lock due to the regenerative torque of the driving motor, the angular acceleration of the wheel rapidly increases on the deceleration side. Therefore, it is possible to estimate the friction coefficient between the wheel and the road surface based on the regenerative torque at the timing when the angular acceleration of the wheel rapidly increases on the deceleration side. For example, on a road surface with a small friction coefficient such as a frozen road surface, the regenerative torque when the angular acceleration of the wheel rapidly increases on the deceleration side appears small, while on a road surface with a large friction coefficient such as a dry road surface, the regenerative torque when the angular acceleration of the wheel rapidly increases on the deceleration side appears large.

Explanation of Signs

[0073] 10 Vehicle control device 11 Vehicle 12L, 12R Front wheels (first wheels) 14L, 14R Rear wheels (second wheels) 16 Front motor (first driving motor) 18 Rear motor (second driving motor) 20 Control system 70 Processor 71 Memory 80 Vehicle control device 81 Vehicle 82L Left front wheel (first wheel, second wheel) 82R Right front wheel (first wheel, second wheel) 83L Left rear wheel (first wheel, second wheel) 83R Right rear wheel (first wheel, second wheel) 84 Left front motor (first driving motor, second driving motor) 85 Right front motor (first driving motor, second driving motor) 86 Left rear motor (first driving motor, second driving motor) 87 Right rear motor (first driving motor, second driving motor) 98 Control system Fμ Coefficient of friction (first coefficient of friction) Rμ Coefficient of friction (second coefficient of friction) FLμ Coefficient of friction (first coefficient of friction, second coefficient of friction) FRμ Coefficient of friction (first coefficient of friction, second coefficient of friction) RLμ Coefficient of friction (first coefficient of friction, second coefficient of friction) RRμ Coefficient of friction (first coefficient of friction, second coefficient of friction) Δμ1~Δμ3 Difference μ1 Threshold value (first threshold value) Xμ Threshold value (second threshold value) Sf, Sr Road surface Td, Td1~Td3 Delay time (first delay time, second delay time) T1 Target motor torque (target torque)

Claims

1. A vehicle control device provided in a vehicle, a first driving motor connected to a first wheel, a second driving motor connected to a second wheel, comprising a processor and a memory connected to be communicable with each other, and a control system for controlling the first driving motor and the second driving motor, and having the control system estimates a first friction coefficient between the first wheel and the road surface and a second friction coefficient between the second wheel and the road surface, the control system when starting the vehicle, at least one of the first friction coefficient and the second friction coefficient is less than a first threshold value, and a difference between the first friction coefficient and the second friction coefficient exceeds a second threshold value, when the first friction coefficient is smaller than the second friction coefficient, after increasing the driving torque of the second driving motor and after elapsing a first delay time set based on the first friction coefficient, increasing the driving torque of the first driving motor, while when the second friction coefficient is smaller than the first friction coefficient, after increasing the driving torque of the first driving motor and after elapsing a second delay time set based on the second friction coefficient, increasing the driving torque of the second driving motor, A vehicle control device.

2. In the vehicle control device according to claim 1, the first delay time is set to be longer as the first friction coefficient becomes smaller, the second delay time is set to be longer as the second friction coefficient becomes smaller, A vehicle control device.

3. In the vehicle control device according to claim 1 or 2, the control system when starting the vehicle, at least one of the first friction coefficient and the second friction coefficient is less than the first threshold value, and a difference between the first friction coefficient and the second friction coefficient exceeds the second threshold value, when the first friction coefficient is smaller than the second friction coefficient, controls the driving torque of the second driving motor to be smaller than a target torque based on a required driving force, when the second friction coefficient is smaller than the first friction coefficient, controls the driving torque of the first driving motor to be smaller than a target torque based on a required driving force, A vehicle control device.

4. In the vehicle control device according to any one of claims 1 to 3, the control system When at least one of the first friction coefficient and the second friction coefficient is less than the first threshold value and the difference between the first friction coefficient and the second friction coefficient is less than the second threshold value during vehicle start, the power running torque of the first driving motor is controlled to be smaller than the target torque based on the required driving force, and the power running torque of the second driving motor is controlled to be smaller than the target torque based on the required driving force. A vehicle control device.

5. In the vehicle control device according to claim 3 or 4, the power running torque of the first driving motor decreases as the first friction coefficient decreases, and the power running torque of the second driving motor decreases as the second friction coefficient decreases. A vehicle control device.

Images