WO2011132335A1 - Electric vehicle, braking program, and control method and control device of electric vehicle - Google Patents

Abstract

Even if the coefficients of friction of the respective road surfaces on which the front wheels and the rear wheels travel are different, the disclosed electric vehicle can easily secure stable travelling characteristics under various road and travelling conditions by generating optimal braking/driving power between the tires and the road surface. The electric vehicle (1), which has two motors (3) that independently drive the front and back wheels (2) with a differential gear (4) therebetween, is provided with: a road surface friction coefficient (µ) estimation means that estimates a first and second coefficient of friction of the respective road surfaces that the front and back wheels are travelling over; a slip ratio upper limit setting means that sets a first and second predetermined value for the slip ratio of each front and back wheel in accordance with the first and second coefficients of friction; a slip ratio computation means that computes the slip ratio of each wheel; and a braking/driving power control means that controls the braking/driving power of the front wheel motor (3f) in a manner so that the higher slip ratio of the slip ratios of the left and right front wheels becomes the first predetermined value, or controls the braking/driving power of the rear wheel motor (3r) in a manner so that the higher slip ratio of the slip ratios of the left and right rear wheels becomes the second predetermined value.

Description

Electric vehicle, braking program, and control device and control method for electric vehicle

The present invention relates to an electric vehicle, a braking program, and a control device and a control method for an electric vehicle in which front and rear wheels are independently driven by two electric motors.

Conventionally, a braking / driving control device for a vehicle in which front and rear wheels are independently driven by two electric motors is known (for example, see Patent Document 1).

This vehicle braking / driving control device estimates the slip ratio of the front wheels and the rear wheels, and exceeds the maximum braking / driving force when the slip ratios of the front wheels and the rear wheels do not exceed the corresponding threshold values for the front wheels and rear wheels. The target braking / driving force is calculated according to the driver's required braking / driving force within the range, and when the front wheel and rear wheel slip rates exceed the corresponding front wheel threshold and rear wheel threshold, the front wheel and rear wheel The braking / driving force at the time of slip occurrence is set as the target braking / driving force of the front wheels and the rear wheels.

Conventionally, an electric vehicle in which each of the four wheels is driven by a motor is known (for example, see Patent Document 2).

This electric vehicle is steered on the basis of four motors for driving each of the four wheels, a yaw rate sensor for detecting the rotational speed around the Z-axis, that is, the turning speed of the vehicle body, and the turning speed of the vehicle body detected by the yaw rate sensor. And a control device that controls the torques of the four motors so as to obtain a turning acceleration corresponding to the angle.

JP 2008-228407 A JP 2005-184911 A

However, according to the conventional braking / driving control device for a vehicle described in Patent Document 1, the braking / driving force of each wheel is controlled with the same friction coefficient of the road surface on which the front and rear wheels travel, There is a possibility that wheel spin or wheel lock may occur when the road surface conditions of the front and rear wheels are different.

Further, according to the conventional electric vehicle described in Patent Document 2, each motor of the four wheels is controlled independently, and therefore, when various road surfaces and travel conditions change, the left and right wheels of the front and rear wheels are controlled. Since a power change occurs, there is a problem that an acceleration change from a turning acceleration corresponding to the steering angle suddenly occurs when the vehicle turns, and control for maintaining vehicle stability becomes complicated.

Accordingly, an object of the present invention is to provide an electric vehicle, a braking program, and an electric vehicle capable of generating an optimal braking / driving force between tire road surfaces even when the friction coefficients of the road surfaces on which the front wheels and the rear wheels are traveling are different. The present invention provides a control device and a control method.

Another object of the present invention is to provide an electric vehicle, a braking program, and a control device and control method for an electric vehicle that can easily ensure stable traveling performance under various road surfaces and traveling conditions. is there.

In order to achieve the above object, one aspect of the present invention provides a first electric motor that transmits braking / driving force to the left and right wheels on the front wheel side via the first differential, and the left and right wheels on the rear wheel side. A second electric motor that transmits braking / driving force via the second differential, a first friction coefficient of the road surface on which the front wheels travel, and a second friction coefficient of the road surface on which the rear wheels travel. An estimation unit for estimating; a first predetermined value of the slip ratio of the front wheel according to the first friction coefficient; and a second predetermined value of the slip ratio of the rear wheel according to the second friction coefficient. A setting unit for setting a value, a calculation unit for calculating the slip ratio of each wheel, and the higher slip ratio of the slip ratios of the left and right wheels on the front wheel side becomes the first predetermined value. Control the braking / driving force of the first electric motor, or out of the slip ratio of the left and right wheels on the rear wheel side There way slip ratio provides an electric vehicle and a control unit for controlling the longitudinal force of the second electric motor such that the second predetermined value.

According to the present invention, an optimal braking / driving force can be generated between the tire road surfaces even when the friction coefficients of the road surfaces on which the front wheels and the rear wheels travel are different. In addition, it is possible to easily ensure stable running performance under various road surfaces and running conditions.

FIG. 1 is a block diagram conceptually showing the structure of the electric vehicle according to the first embodiment of the present invention. FIG. 2 is a block diagram functionally showing the control device. FIG. 3 is a diagram showing the relationship between the driving force and braking force and the slip ratio. FIG. 4 is a diagram for explaining a method of distributing the braking force to the front wheels and the rear wheels. FIG. 5 is a flowchart showing an example of braking / driving force control of the electric vehicle according to the first embodiment of the present invention. FIG. 6 is a block diagram conceptually showing the structure of the electric vehicle according to the second embodiment of the present invention. FIG. 7 is a block diagram functionally showing the control device according to the second embodiment of the present invention. FIG. 8 is a diagram for explaining the braking / driving force control according to the steering angle. FIG. 9 is a plan view showing a state in which the vehicle body is about to turn. FIG. 10 is a plan view showing a state in which the vehicle body is turning and moving in the lateral direction. FIG. 11 is a flowchart showing an example of control of braking / driving force of the electric vehicle according to the second embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in each figure, about the component which has the substantially same function, the same code | symbol is attached | subjected and the duplicate description is abbreviate | omitted.

[First Embodiment]
FIG. 1 is a block diagram conceptually showing the structure of the electric vehicle according to the first embodiment of the present invention. In FIG. 6 and FIG. 6 to be described later, additional symbols f, r, fr, which indicate whether the position of the component is the front wheel side or the rear wheel side, the right side or the left side of the front wheel side, the right side or the left side of the rear wheel side, fl, rr, and rl are attached to the constituent elements. Further, when it is not necessary to particularly distinguish the positions of the constituent elements, the words “for front wheels” and “for rear wheels” indicating the additional symbols and positions may be omitted.

The electric vehicle 1 includes a front wheel motor 3f as a first electric motor that drives front wheels 2fr and 2fl via a front wheel differential 4f and axles 5fr and 5fl as a first differential, and a rear wheel. 2rr, 2rl as rear differential gear 4r as second differential device and rear wheel motor 3r as second electric motor driven via axles 5rr, 5rl, and drive energy source of electric vehicle 1 As a power supply unit 7, a front wheel inverter 8 f and a rear wheel inverter 8 r that convert electric power from the power supply unit 7 into AC power, and a first drive circuit that outputs signals corresponding to the target torque to the inverters 8 f and 8 r The front wheel drive circuit 9f and the rear wheel drive circuit 9r as the second drive circuit, and the front wheel motor 3f and the rear wheel motor 3 by outputting command signals to the drive circuits 9f and 9r. Was a control unit 10 for controlling independently of each other, a wheel independent drive electric vehicles back and forth.

The electric vehicle 1 includes an accelerator pedal 12 and a brake pedal 13 operated by a driver, operating means such as a shift lever 14 for designating forward and reverse, a front wheel motor 3f and a rear wheel motor 3r. Encoders 16f and 16r for detecting the respective rotational speeds, mechanical brakes 18fr, 18fl, 18rr and 18rl for braking the rotation of the axles 5fr, 5fl, 5rr and 5rl, and two cameras 20fr provided on the front side of the vehicle body 25, 20rl, a camera 21 provided on the rear side of the vehicle body 25, an accelerator sensor 22 for detecting the amount of depression of the accelerator pedal 12, a brake sensor 23 for detecting the amount of depression of the brake pedal 13, and the positions of the shift lever 14 A shift sensor 24 to detect and an acceleration sensor to detect the acceleration of the vehicle body 25 It includes a degree detecting unit) 26, a temperature sensor 27f for detecting the motor 3f, a temperature of 3r respectively, and 27r, the wheel speed sensor 28fr for detecting the rotational speed of the wheel 2, 28fl, 28rr, and 28RL.

In this specification, an “electric vehicle” is an automobile having an electric motor for driving front wheels and rear wheels, and has both an electric motor and an engine as power sources for wheels, and can be regeneratively braked by the electric motor. It is a concept that includes a hybrid car. Here, “automobile” is a concept including not only passenger cars but also buses and freight cars, regardless of whether they are ordinary cars, large cars, and oversized cars. Further, in this specification, “braking / driving force” may mean both braking force for decelerating the vehicle and driving force for accelerating the vehicle or only one of them.

Next, the details of each part will be described.

(Power supply system)
The power supply unit 7 includes a battery 70, a front wheel smoothing capacitor 71f, a rear wheel smoothing capacitor 71r, a voltage sensor 72f for detecting the voltage (inverter input voltage) of the front wheel smoothing capacitor 71f, and a rear wheel smoothing capacitor 71r. Is provided with a voltage sensor 72r for detecting the voltage (inverter input voltage) and a battery capacity sensor 73 for detecting the storage capacity of the battery 70.

The battery 70 is a high voltage battery that can output electric power for driving the front wheel motor 3f and the rear wheel motor 3r. In addition to the battery 70, a primary battery such as a dry battery, a fuel cell, or the like may be used as a drive energy source for the electric vehicle 1.

(Drive system)
As the front wheel motor 3f and the rear wheel motor 3r, for example, various motors such as a synchronous motor and an induction motor can be used. The rotation of the motor 3 is transmitted to the axle 5 via the differential device 4 on each of the front wheel side and the rear wheel side. The axle 5 rotates integrally with the wheel 2. That is, the electric vehicle 1 has two torque generation sources corresponding to the front wheels 2fr and 2fl and the rear wheels 2rr and rl so that the front wheels 2fr and 2fl and the rear wheels 2rr and rl can be controlled independently of each other. The output torque (motor capacity) generated by the front wheel motor 3f and the rear wheel motor 3r may or may not be equal to each other.

The inverter 8 converts the power from the battery 70 into AC power and outputs a current corresponding to a signal from the drive circuit 9 to the motor 3 to drive the motor 3. Further, the inverter 8 converts AC power generated by the motor 3 into DC power and charges the battery 70 via the capacitors 71f and 71r.

The front wheel drive circuit 9f receives current detection signals from the current sensors 15a, 15b, 15c that detect the current of the primary winding of the front wheel motor 3f. The rear wheel drive circuit 9r receives current detection signals from the current sensors 17a, 17b, and 17c that detect the current of the primary winding of the rear wheel motor 3r. The drive circuits 9 f and 9 r output a signal corresponding to the target torque commanded from the control device 10 to the inverter 8.

The differential devices 4f and 4r can rotate, for example, a pair of side gears connected to the front wheel axles 5fr and 5fl or the rear wheel axles 5rr and 5rl, a plurality of pinion gears engaged with the pair of side gears, and a plurality of pinion gears. A so-called open differential provided with a differential case supported on the front can be used. The braking / driving force of the front wheel motor 3f is distributed to the right front wheel 2fr and the left front wheel 2fl by the front wheel differential 4f. The braking / driving force of the rear wheel motor 3r is distributed to the right rear wheel 2rr and the left rear wheel 2rl by the rear wheel differential 4r. The differential device has a mechanism capable of controlling the distribution ratio of braking / driving force to the front wheel axles 5fr and 5fl or the distribution ratio of braking / driving force to the rear wheel axles 5rr and 5rl by the control device 10. It may be provided.

(Sensor system)
The encoders 16f and 16r detect the rotation speeds of the motors 3f and 3r on the front wheel side and the rear wheel side, respectively, and output a signal corresponding to the detected rotation speed to the control device 10.

The accelerator sensor 22 detects the depression amount of the accelerator pedal 12 and outputs a signal xa corresponding to the detected depression amount to the control device 10.

The brake sensor 23 detects the depression amount of the brake pedal 13, and outputs a signal xb corresponding to the detected depression amount to the control device 10.

The shift sensor 24 detects the position of the shift lever 14 and outputs it to the signal S control device 10 according to the detected position.

The acceleration sensor 26 is provided in the vicinity of the center of gravity position of the vehicle body 25 and detects accelerations a _Y , a _X , and aθ in three directions of the vehicle body 25 in the forward / backward direction, the lateral direction, and the rotational direction (turning direction) around the center of gravity axis. And outputs signals corresponding to the detected accelerations a _Y , a _X , and aθ to the control device 10.

Wheel speed sensors 28fr, 28fl, 28rr, 28rl detect the rotational speed ω of the wheel and output a signal corresponding to the detected rotational speed ω to the control device 10.

The voltage sensors 72f and 72r detect the voltage (inverter input voltage) of the capacitors 71f and 71r, and output a signal corresponding to the detected inverter input voltage to the control device 10.

Battery capacity sensor 73 detects the storage capacity (remaining capacity) of battery 70 and outputs a signal corresponding to the detected storage capacity to control device 10. The battery capacity sensor 73 is obtained by, for example, a method based on the battery terminal voltage (open voltage), a method based on the battery internal resistance, a method based on the integrated value of the battery charge / discharge current, or a combination of these. Thus, the storage capacity of the battery 70 is detected.

(Brake system)
In the electric vehicle 1, an electric brake and a mechanical brake are used in combination. That is, in the electric vehicle 1, a braking force can be generated by the motor 3 as a drive source. The electric brake is, for example, a power generation brake that converts braking energy into heat energy, and a regenerative brake that regenerates electricity generated by braking. In the present embodiment, a regenerative brake is mainly used, but a power generation brake may be used in a low speed region. The regenerative brake regenerates the electric power generated by the motor 3 to the battery 70 via the capacitor 71, thereby generating a braking force.

The mechanical brake 18 is, for example, a drum brake or a disc brake, and presses a brake shoe against a member to be braked by pressurized liquid from the pressure adjustment unit 11 to obtain friction braking by a friction force. The operation of the mechanical brake 18 is controlled independently for each wheel 2 by the control device 10. The brake shoe may be pressed against the member to be braked by an actuator such as a motor.

The pressure adjustment unit 11 is configured to be able to apply a different braking force to each mechanical brake 18 by distributing pressurized liquid to the mechanical brake 18 according to a signal from the control device 10. The pressure adjusting unit 11 and the mechanical brake 18 constitute a friction brake mechanism.

(Imaging system)
The front cameras 20 fr and 20 fl capture the road surface in front of the electric vehicle 1 and output the captured image to the control device 10. The control device 10 detects a change in the road surface based on the images acquired from the cameras 20fr and 20fl, and executes processing related to braking / driving. The imaging regions of the front cameras 20fr and 20fl overlap at least partially with each other. The cameras 20fr and 20fl are constituted by, for example, a CCD (Charge Coupled Device) camera.

The rear camera 21 images the road surface behind the electric vehicle 1 and outputs the captured image to the control device 10. The control device 10 detects a change in the road surface based on the image acquired from the camera 21 and executes processing related to braking / driving. The camera 21 is constituted by a CCD camera, for example.

(Control system)
FIG. 2 is a block diagram functionally showing the control device 10. The control device 10 is configured by a computer, for example, and includes a CPU 100 and a storage unit 110 such as a semiconductor memory or a hard disk.

The control device 10 issues an operation command for performing an operation such as acceleration and deceleration according to operation input information generated by the driver operating the operating means such as the accelerator pedal 12 and the brake pedal 13. The rear wheel drive circuit 9r and the mechanical brake 18 are output to control the driving torque (driving force) and braking torque (braking force) of the front wheel driving system and the rear wheel driving system. Thereby, the electric vehicle 1 can drive | work according to a driver | operator's operation.

The control device 10 calculates the target torque of the front wheel motor 3f and the target torque of the rear wheel motor 3Rr according to the signals from the sensors 22, 23, 24, etc., respectively, and the front wheel drive circuit 9f and the rear wheel drive are calculated. Output to the circuit 9r. On each of the front wheel side and the rear wheel side, the drive circuit 9 outputs a signal corresponding to the target torque commanded from the control device 10 to the inverter 8.

The storage unit 110 stores various data such as a road surface pattern 111, a μ-SrLimit table 112, information on the relationship between braking / driving force and slip ratio as shown in FIG. 3 to be described later, and various programs such as a braking / driving program 113a. Stored.

The CPU 100 operates in accordance with the braking / driving program 113a, so that the road surface friction coefficient μ estimating unit (estimating unit) 101, the slip ratio upper limit value setting unit (setting unit) 102, the slip rate calculating unit (calculating unit) 103, the braking force control. It functions as the means (control unit) 104a and the like.

(Road surface friction coefficient μ estimation means)
The road surface friction coefficient μ estimation means 101 is based on an image captured by the front cameras 20fr and fl (the rear camera 21 when the vehicle is reverse), and the road surface on which the automobile 1 travels is a dry road surface, a wet road surface, a frozen / snow surface. It is determined whether the road surface is a road surface or the like, and a first friction coefficient μf of the road surface on which the front wheels 2fr and 2fl travel and a second friction coefficient μr of the road surface on which the rear wheels 2rr and 2rl travel are estimated. These road surfaces are typical road surfaces with greatly different friction coefficients μ. The determination is performed by pattern matching between the captured image and the road surface pattern 111 captured in advance in each road surface condition. The road surface pattern 111 is stored in the storage unit 110 in association with the friction coefficient μ of the road surface. In addition, you may perform using the well-known technique suitably, such as performing the said determination by determination whether the brightness | luminance etc. exceeded the predetermined threshold value. In addition, the coefficient of friction with the road surface may be estimated in consideration of tire characteristic information (deterioration, type, wheel load, air pressure, etc. of the tire) estimated from the use history such as the travel distance and use period for each tire. . That is, it can be predicted that the tire is deteriorated as the traveling distance of the tire or the period of use is longer, and the coefficient of friction with the road surface may be estimated according to the degree of deterioration of the tire.

(Slip rate upper limit setting means)
FIG. 3 is a diagram showing the relationship between the driving force and braking force and the slip ratio. A solid line L1 indicates a dry road surface, a solid line L2 indicates a wet road surface, and a solid line L3 indicates a frozen / snow road surface. Each of these road surfaces is a typical road surface having a significantly different friction coefficient. The coefficient of friction is, for example, 0.75 on a dry road surface, 0.4 on a wet road surface, and 0.2 on a frozen / snow road surface. As shown in FIG. 2, the storage unit 110 stores a μ-SrLimit table 112 indicating the relationship between the road friction coefficient μ and the slip ratio upper limit value SrLimit. In the μ-SrLimit table 112, for example, the slip ratio upper limit value SrLimit1 (| Sr | = 0.16) is stored corresponding to the dry road surface (μ = 0.75), and the wet road surface (μ = 0.4). ) Is stored in response to the slip ratio upper limit value SrLimit2 (| Sr | = 0.14), and the slip ratio upper limit value SrLimit3 (| Sr | = 0) corresponding to the frozen / snow road surface (μ = 0.2). .12) is stored.

The slip ratio upper limit setting means 102 refers to the μ-SrLimit table 112 in the storage unit 110 based on the first and second friction coefficients μf and μr of the road surface estimated by the road surface friction coefficient μ estimation means 101, A slip ratio upper limit value SrLimit-f as a first predetermined value for the front wheels 2fr and 2fl and a slip ratio upper limit value SrLimit-r as a second predetermined value for the rear wheels 2rr and 2rl are set. For example, the slip ratio upper limit value SrLimit is set to a value near the maximum value of the braking / driving force that can be exhibited according to each road surface condition in FIG. 3, but is not limited to a value near the maximum value. The slip ratio upper limit value SrLimit can be set to a slip ratio at which a braking / driving force higher than 70 to 90% of the maximum braking force that can be exhibited according to the friction coefficient of the road surface, for example.

The slip ratio upper limit setting means 102 is a timing at which the front cameras 20fr and 20fl (the rear camera 21 when the vehicle is reverse) images the road surface, and the front wheels 2fr and 2fl and the rear wheels 2rr and 2rl enter the imaged road surface. To set the slip ratio upper limit values SrLimit-f and SrLimit-r for the front wheels 2fr and 2fl and the rear wheels 2rr and 2rl, respectively. For example, when the front wheels 2fr and 2fl enter a wet road surface while traveling on a dry road surface, a slip ratio upper limit value (for example, | Sr | = 0.14) corresponding to the wet road surface is set for the front wheels 2fr and 2fl. For the rear wheels 2rr and 2rl, a slip ratio upper limit value (for example, | Sr | = 0.16) corresponding to the dry road surface is set. When the vehicle moves forward, intermediate values between the friction coefficient estimated from the images captured by the front cameras 20fr and 20fl and the friction coefficient estimated from the images captured by the rear camera 21 are used as the friction coefficient and slip ratio of the rear wheels. It may be used as an upper limit value, or an intermediate value thereof may be used as a front wheel friction coefficient or a slip ratio upper limit value when the vehicle is moving backward.

(Slip rate calculation means)
The slip ratio calculating means 103 calculates the slip ratio Sr of the wheel 2 during driving by the following formula, where V is the vehicle body speed, ω is the rotational speed of the wheel 2, and R is the radius of the wheel 2.
Sr = (Rω−V) / Rω (1)

Moreover, the slip ratio calculating means 103 calculates the slip ratio Sr of the wheel 2 at the time of braking by the following formula.
Sr = (Rω−V) / V (2)

As understood from the equation (1), when the slip ratio Sr becomes 1.0 at the time of driving, V = 0 and the wheel spin is generated. As understood from the equation (2), when the slip ratio Sr becomes −1.0 during braking, ω = 0 and a wheel lock is generated. That is, the state where the absolute value of the slip ratio Sr is 1 is a state where any braking / driving force (driving force or braking force) cannot be transmitted to the road surface. The state where the slip ratio Sr is 0 is a state where there is no slip between the wheel 2 and the road surface.

(Braking / driving force control means)
The braking / driving force control means 104a uses the μ-SrLimit table 112, the slip ratio control for controlling the slip ratio to a certain target value based on the relation information between the braking / driving force and the slip ratio as shown in FIG. Carry out wheel lock and wheel spin suppression control. Hereinafter, those controls will be described.

<Slip rate control>
The braking / driving force control means 104a compares the slip ratio | Sr | between the left and right wheels, and the larger slip ratio | Sr | becomes the slip ratio upper limit values SrLimit-f and SrLimit-r set for the front and rear wheels, respectively. Thus, the driving force of the motors 3f and 3r or the braking force of the electric brake and the mechanical brake 18 of the motors 3f and 3r is controlled. Further, the braking / driving force control means 104a controls the braking / driving force within a range not exceeding the braking / driving force depending on the depression amount of the accelerator pedal 12 or the brake pedal 13.

If there is a difference in motor capacity between the front wheel motor 3f and the rear wheel mower 3r, the braking / driving force control means 104a determines the slip ratio of the left and right wheels with the larger motor capacity as the smaller motor capacity. The braking / driving force of the motors 3f and 3r may be controlled in preference to the slip ratio of the left and right wheels. For example, the braking / driving force control means 104 may distribute the braking / driving force to the front and rear wheels according to the ratio of the motor capacity of the motors 3f and 3r.

<Control of wheel lock and wheel spin suppression with load transfer>
FIG. 4 is a diagram for explaining a method of distributing braking force to the front wheels 2fr, 2fl and the rear wheels 2rr, 2rl in the electric vehicle 1.

As shown in FIG. 4, the braking force Fcar when the electric vehicle 1 decelerates at an acceleration a _Y is
Fcar = M × a _Y Expression (3)
It becomes. Here, M is the mass (body mass) of the entire electric vehicle 1.

The load movement amount Z at that time is obtained by the following equation (4) in which the moment around the center of gravity G of the electric vehicle 1 generated by the braking force Fcar is converted to the vertical load at the contact point of the front wheels 2fr and 2fl and the rear wheels 2rr and 2rl. It is done.
Z = Fcar × Hcar / Lcar (4)
Here, Hcar is the height of the center of gravity G of the electric vehicle 1 from the ground contact surface, and Lcar is the wheel base of the electric vehicle 1.

When the front wheel load when the electric vehicle 1 is stopped is Wf, the rear wheel load is Wr, and the friction coefficient of the road surface is μ, the braking force of the front and rear wheels that balances the friction force, that is, the front wheels 2fr, 2fl. The maximum braking force Ffmax and the maximum braking force Frmax of the rear wheels 2rr and 2rl are expressed by the following equations (5) and (6), respectively.
Ffmax = μ (Wf + Z) (5)
Frmax = μ (Wr−Z) (6)

Therefore, if the operation of the motor 3 and the mechanical brake 18 is controlled so that the braking force by the motor 3 and the mechanical brake 18 on the front wheel side and the rear wheel side becomes the maximum braking force Ffmax and the maximum braking force Frmax, respectively. The entire vehicle 1 has the largest braking force, and wheel lock can be suppressed. The above is the explanation at the time of deceleration, but the same is true at the time of acceleration, and wheel spin can be suppressed by controlling so as to obtain an optimum driving force based on the load movement.

For example, when the electric vehicle 1 decelerates when moving forward, the load on the front wheel side increases and the load on the rear wheel side decreases due to load movement corresponding to the magnitude of acceleration. The braking force control means 104 sets the front wheel slip ratio upper limit value SrLimit to a slip ratio at which a braking force higher than 70 to 90% of the maximum braking force that can be exhibited according to an increase in wheel load, for example, is exhibited. Can do. Further, by correcting the rear wheel side slip ratio upper limit value SrLimit so as to limit the braking force according to the decrease in the load on the rear wheel side, a braking force larger than that on the rear wheel side is generated on the front wheel side, A more appropriate braking force can be applied to each wheel 2.

In addition, when the electric vehicle 1 is accelerated when moving forward, the load on the front wheel side is reduced and the load on the rear wheel side is increased by moving the load according to the magnitude of the acceleration. The braking force control means 104 sets the rear wheel slip ratio upper limit value SrLimit to a slip ratio at which a driving force higher than 70 to 90% of the maximum braking force that can be exhibited in response to an increase in wheel load, for example. be able to. Further, by correcting the front wheel side slip ratio upper limit value SrLimit so as to limit the driving force according to the decrease in the load on the front wheel side, a larger driving force is generated on the rear wheel side than on the front wheel side, and more appropriately Drive force can be applied to each wheel 2.

(Operation of the first embodiment)
Next, braking / driving force control of the electric vehicle 1 will be described with reference to FIG. FIG. 4 is a flowchart illustrating an example of braking / driving force control of the electric vehicle 1.

When the driver depresses the accelerator pedal 12, the accelerator sensor 22 outputs a signal xa corresponding to the depression amount of the accelerator pedal 12 to the control device 10. When the driver depresses the brake pedal 13, the brake sensor 23 outputs a signal xb corresponding to the depression amount of the brake pedal 13 to the control device 10.

The braking / driving force control means 104a determines whether or not there is an accelerator or brake operation based on the presence or absence of signals xa and xb from the accelerator sensor 22 or the brake sensor 23 (S1).

When the accelerator or brake is operated (S1: Yes), the braking / driving force control means 104a applies a braking / driving force corresponding to the operation amount of the accelerator or the brake to each wheel 2 (S2).

That is, the braking / driving force control means 104a calculates a driving torque corresponding to the depression amount based on the signal xa from the accelerator sensor 22, distributes the calculated driving torque to the front wheel side and the rear wheel side, and distributes the driving torque distributed. Is output to the corresponding drive circuits 9f and 9r. The drive circuits 9f and 9r drive the motors 3f and 3r by the inverters 8f and 8r based on the control signal from the braking / driving force control means 104. The motors 3f and 3r transmit the driving force to the wheels 2 via the differential devices 4f and 4r.

The braking / driving force control means 104 calculates a braking torque corresponding to the depression amount based on the signal xb from the brake sensor 23, distributes the calculated braking torque to the front wheel side and the rear wheel side, and responds to the distributed braking torque. The control signal is output to the pressure adjustment unit 11 and the drive circuits 9f and 9r. The pressure adjustment unit 11 distributes the pressurized liquid based on the control signal from the braking / driving force control means 104 and operates the mechanical brake 18. The drive circuits 9f and 9r operate the electric brake by the inverters 8f and 8r based on the control signal from the braking / driving force control means 104. A braking force by the mechanical brake 18 and the electric brake is applied to each wheel 2.

Next, the road surface friction coefficient μ estimation means 101 estimates a first friction coefficient μf on the road surface on the front wheels 2fr and 2fl side on which the electric vehicle 1 travels and a second friction coefficient μr on the road surface on the rear wheels 2rr and 2rl side. (S3). For example, the first and second friction coefficients μf and μr of the road surface are estimated by pattern matching between the images captured by the front cameras 20 fr and fl and the road surface pattern 111 stored in the storage unit 110.

Next, the slip ratio upper limit setting means 102 sets the slip ratio upper limit values SrLimit-f and SrLimit-r for the front wheels 2fr and 2fl and the rear wheels 2rr and 2rl corresponding to the estimated road friction coefficients μf and μr, respectively. Set with reference to the SrLimit table 112 (S4).

Then, slip rate calculating means 103, on the basis of the signals corresponding to the acceleration a _Y longitudinal direction of the propulsion of the vehicle body 25 from the acceleration sensor 26, promoting longitudinal direction by integrating the acceleration a _Y of the propulsion longitudinal direction of the vehicle body 25 Vehicle body speed V is obtained.

Subsequently, the slip ratio calculating means 103 obtains the rotational speed ω of the wheel 2 based on a signal corresponding to the rotational speed ω of the wheel 2 from the wheel speed sensor 28.

Next, the slip ratio calculating means 103 calculates the slip ratio Sr of each wheel 2 from the radius R of the wheel 2, the rotational speed ω of the wheel 2, and the vehicle body speed V using the above formula (2) (S5).

Next, the braking force control means 104a compares the slip ratio | Sr | between the left and right wheels (S6). That is, the slip ratios | Sr | of the front wheels 2fr and 2fl are compared, and the slip ratios | Sr | of the rear wheels 2rr and 2rl are compared.

Next, the braking force control means 104a compares the larger slip ratio | Sr | with the set slip ratio upper limit values SrLimit-f and SrLimit-r (S7). That is, the larger slip ratio | Sr | of the front wheels 2fr and 2fl is compared with the slip ratio upper limit value SrLimit-f set for the front wheels 2fr and 2fl, and the larger slip ratio of the rear wheels 2rr and 2rl | Sr | is compared with the slip ratio upper limit value SrLimit-r set for the rear wheels 2rr and 2rl.

As a result of the comparison in step S7, if the slip ratio | Sr | is smaller than the slip ratio upper limit values SrLimit-f and SrLimit-r, the braking / driving force on the front wheel or rear wheel side is increased (S8). That is, when the accelerator pedal 12 is operated in step S1, the driving force of the front wheel motor 3f or the rear wheel motor 3r is increased. When the brake pedal 13 is operated in step S1, the braking force of the electric brake and mechanical brakes 18fr and 18fl of the front wheel motor 3f is increased, or the electric brake and mechanical brakes 18rr and 18rl of the rear wheel motor 3r are increased. Increase the braking force.

As a result of the comparison in step S7, if the slip ratio | Sr | is larger than the slip ratio upper limit values SrLimit-f and SrLimit-r, the braking / driving force on the front or rear wheel side is decreased (S9). That is, when the accelerator pedal 12 is operated in step S1, the driving force of the front wheel motor 3f or the rear wheel motor 3r is decreased. When the brake pedal 13 is operated in step S1, the braking force of the electric brake and mechanical brakes 18fr and 18fl of the front wheel motor 3f is decreased, or the electric brake and mechanical brakes 18rr and 18rl of the rear wheel motor 3r are reduced. Reduce the braking force.

If the slip ratio | Sr | is equal to the upper limit value SrLimit (SrLimit-f, SrLimit-r) as a result of the comparison in step S7, a braking / driving force corresponding to the accelerator or brake operation amount is applied to the wheel 2. (S2).

(Effects of the first embodiment)
According to the first embodiment, the following effects are obtained.
(A) Even when the friction coefficients of the road surfaces on which the front wheels and the rear wheels travel are different, the maximum braking / driving force can be generated between the tire road surfaces.
(B) Since the maximum braking / driving force can be exhibited, energy-saving driving is possible.
(C) Stable running is possible by suppressing wheel spin and wheel lock when starting and stopping on a road surface with a low friction coefficient (low μ road).

[Second Embodiment]
FIG. 6 is a block diagram conceptually showing the structure of the electric vehicle according to the second embodiment of the present invention. Since the present embodiment is mainly different from the first embodiment in the braking / driving control means and the braking / driving program, the differences will be mainly described.

As in the first embodiment, the electric vehicle 1 includes a front wheel differential 4f, 4r, a front wheel motor 3f, a rear wheel motor 3r, a power supply unit 7, a front wheel inverter 8f, and a rear wheel inverter 8r. A front wheel drive circuit 9f, a rear wheel drive circuit 9r, and a control device 10.

Further, as in the first embodiment, the electric vehicle 1 includes operating means such as an accelerator pedal 12, a brake pedal 13, and a shift lever 14, encoders 16f and 16r, mechanical brakes 18fr and 18fl, cameras 20fr and 20r, 21, an accelerator sensor 22, a brake sensor 23, a shift sensor 24, an acceleration sensor (acceleration detection unit) 26, temperature sensors 27f and 27r, and wheel speed sensors 28fr, 28fl, 28rr, and 28rl, and a steering angle of the steering wheel 19 And a steering angle sensor 29 for detecting.

The steering angle sensor 29 detects the steering angle γ of the steering wheel 19 and outputs a signal corresponding to the detected steering angle γ to the control device 10.

(Control system)
FIG. 7 is a block diagram functionally showing the control device 10. The control device 10 is configured by a computer, for example, and includes a CPU 100 and a storage unit 110 such as a semiconductor memory or a hard disk.

The control device 10 issues an operation command for performing an operation such as acceleration and deceleration according to operation input information generated by the driver operating the operating means such as the accelerator pedal 12 and the brake pedal 13. The rear wheel drive circuit 9r and the mechanical brake 18 are output to control the driving torque (driving force) and braking torque (braking force) of the front wheel driving system and the rear wheel driving system. Thereby, the electric vehicle 1 can drive | work according to a driver | operator's operation.

The control device 10 calculates the target torque of the front wheel motor 3f and the target torque of the rear wheel motor 3Rr according to the signals from the sensors 22, 23, 24, etc., respectively, and the front wheel drive circuit 9f and the rear wheel drive are calculated. Output to the circuit 9r. On each of the front wheel side and the rear wheel side, the drive circuit 9 outputs a signal corresponding to the target torque commanded from the control device 10 to the inverter 8.

The storage unit 110 includes a road surface pattern 111, a μ-SrLimit table 112, information on the relationship between braking / driving force and slip rate as shown in FIG. 3 to be described later, a threshold value aθ _th 115 of acceleration (turning acceleration) aθ in the turning direction, lateral Various data such as a direction acceleration a _X being a threshold value a _Xth 116 and various programs such as a braking / driving program 113b are stored.

The CPU 100 operates in accordance with the braking / driving program 113b, so that the road surface friction coefficient μ estimating unit 101, the slip ratio upper limit setting unit 102, the slip rate calculating unit (slip rate calculating unit) 103, and the braking / driving force control unit (control unit). 104b or the like.

(Braking / driving force control means)
The braking / driving force control means 104b determines whether or not the slip ratio Sr calculated by the slip ratio calculating means 103 is equal to or less than the slip ratio upper limit value SrLimit. In addition, when the braking / driving force control means 104b compares the slip ratio, the absolute value is used. Then, the braking / driving force control means 104b performs slip ratio control, meandering to control the slip ratio to a certain target value based on the μ-SrLimit table 112, the relation information between the braking / driving force and the slip ratio as shown in FIG. Serpentine suppression control that suppresses the wheel, wheel lock accompanying load movement, wheel spin suppression control, braking / driving force control according to the steering angle, and the like are performed. Hereinafter, those controls will be described.

<Slip rate control>
The braking / driving force control means 104b exerts the driving force of the electric motor 3 according to the depression amount of the accelerator pedal 12 and the depression amount of the brake pedal 13 when the slip ratio of each wheel 2 is equal to or less than the slip ratio upper limit value SrLimit. Accordingly, both the braking force by the mechanical brake 18 and the braking force of the electric brake by the drive circuit 9 are exhibited. Further, the braking / driving force control means 104, for example, on a low μ road with a small friction coefficient, one of the slip rates of each wheel 2 (including the case where a plurality of wheels 2 are simultaneously used) sets the slip rate upper limit value SrLimit. When exceeded, the driving force of the electric motor 3 is controlled so that the slip ratio exceeding the slip ratio upper limit value SrLimit is less than or equal to the slip ratio upper limit value SrLimit, regardless of the depression amount of the accelerator pedal 12, and the brake pedal 13 is depressed. Regardless of the amount, the braking force by the electric brake and the braking force by the mechanical brake 18 are controlled so that the slip rate exceeding the slip rate upper limit value SrLimit is equal to or less than the slip rate upper limit value SrLimit. The braking / driving force control means 104 may determine the braking / driving force control based on the larger slip ratio by determining which of the slip ratios of the left and right wheels is larger.

<Meander suppression control>
In the braking / driving force control means 104b, the slip rate of one of the wheels 2 exceeds the slip rate upper limit value, and the turning acceleration aθ detected by the acceleration sensor 26 exceeds the threshold value aθth (predetermined acceleration). Control to reduce the braking / driving force of the electric motors 3f, 3r corresponding to the front wheels 2fr, 2fl or the rear wheels 2rr, 2rl to which the one wheel 2 belongs so as to suppress the movement (meandering) of the vehicle body 25 in the turning direction. , And control to increase the braking / driving force of the electric motors 3f, 3r corresponding to the rear wheels 2rr, 2rl or the front wheels 2fr, 2fl to which the one wheel 2 does not belong. Only one of the two controls may be performed.

Further, the braking / driving force control means 104b exceeds the slip ratio upper limit value of at least one of the wheels 2, and the turning acceleration aθ and the lateral acceleration a _X detected by the acceleration sensor 26 are the respective threshold values aθ. _{When th} and the threshold value a _Xth (predetermined acceleration) are exceeded, the braking / driving forces of the electric motors 3f and 3r are controlled so as to suppress the turning and lateral movement (meandering) of the vehicle body 25.

<Control of wheel lock and wheel spin suppression with load transfer>
Since it is the same as that of 1st Embodiment, description is abbreviate | omitted.

<Braking / driving force control according to steering angle>
FIG. 8 is a diagram for explaining the braking / driving force control according to the steering angle. In the figure, ωfr, ωfl, ωrr, ωrl indicate the rotational speed of each wheel, and γ indicates the steering angle. The braking / driving force control means 104b controls the braking / driving force of the front wheels 2fr, 2fl according to the friction coefficient of the road surface (wheel slip ratio), so that the total braking / driving force of the front and rear wheels does not change. Control is performed to compensate with a braking / driving force of 2 rl. For example, when the driver operates the steering wheel 19 in the right direction, the front wheel differential speed 4w has a relationship of ωfl> ωfr by the front wheel differential device 4f. When the braking / driving force of the front wheel motor 3f is reduced by the control, control for increasing the braking / driving force of the rear wheel motor 3r is performed in order to compensate the corresponding braking / driving force on the rear wheels 2rr, 2rl side. Thereby, a stable driving force can be obtained.

(Operation of Second Embodiment)
Next, the operation of the electric vehicle 1 will be described with reference to FIG. 9, FIG. 10, and FIG. FIG. 9 is a plan view showing a state in which the vehicle body 25 is about to turn. FIG. 10 is a plan view showing a state where the vehicle body 25 is turning and moving in the lateral direction. FIG. 11 is a flowchart illustrating an example of control of braking / driving force of the electric vehicle 1. In FIGS. 96 and 107, Srfr and Srfl indicate the slip ratio of the front wheel, and Srrr and Srrl indicate the slip ratio of the rear wheel.

When the driver steps on the accelerator pedal 12, the accelerator sensor 22 outputs a signal corresponding to the amount of depression of the accelerator pedal 12 to the control device 10. When the driver steps on the brake pedal 13, the brake sensor 23 outputs a signal corresponding to the amount of depression of the brake pedal 13 to the control device 10.

At the time of driving, the braking / driving force control means 104b calculates the driving torque according to the depression amount based on the signal from the accelerator sensor 22, and calculates the driving torque calculated so as to obtain the turning acceleration according to the steering angle as the front wheel side. Distribute to the rear wheel side. The CPU 100 outputs a control signal corresponding to the driving torque distributed to the front wheel side to the front wheel driving circuit 9f, and outputs a control signal corresponding to the driving torque distributed to the rear wheel side to the rear wheel driving circuit 9r. The front wheel drive circuit 9f drives the front wheel motor 3f by the front wheel inverter 8f based on a control signal from the control device 10. The rear-wheel drive circuit 9r drives the rear-wheel motor 3r by the rear-wheel inverter 8r based on a control signal from the control device 10.

During braking, the braking / driving force control means 104b calculates a braking torque corresponding to the depression amount based on a signal from the brake sensor 23, and distributes the calculated braking torque to the mechanical brake and the electric brake. The braking / driving force control means 104b outputs a control signal corresponding to the braking torque distributed to the mechanical brake to the pressure adjustment unit 11, and outputs a control signal corresponding to the braking torque distributed to the electric brake to the drive circuits 9f and 9r. . The pressure adjusting unit 11 distributes the pressurized liquid based on the control signal from the braking / driving force control means 104b and operates the mechanical brake 18. The drive circuits 9f and 9r operate the electric brake by the inverters 8f and 8r based on the control signal from the braking / driving force control means 104.

Next, the road surface friction coefficient μ estimation means 101 estimates the friction coefficient μ of the road surface on which the electric vehicle 1 travels, as in the first embodiment. For example, the road surface friction coefficients μf and μr are estimated by pattern matching between the images captured by the front cameras 20fr and fl and the road surface pattern 111 stored in the storage unit 110 (S11).

Next, as in the first embodiment, the slip ratio upper limit value setting means 102 sets the slip ratio upper limit values SrLimt-f and SrLimt-r corresponding to the estimated road friction coefficients μf and μr to μ−SrLimit. Setting is made with reference to the table 112 (S12).

Then, slip rate calculating means 103, on the basis of the signals corresponding to the acceleration a _Y longitudinal direction of the propulsion of the vehicle body 25 from the acceleration sensor 26, promoting longitudinal direction by integrating the acceleration a _Y of the propulsion longitudinal direction of the vehicle body 25 Vehicle body speed V is obtained.

Subsequently, the slip ratio calculating means 103 obtains the rotational speed ω of the wheel 2 based on a signal corresponding to the rotational speed ω of the wheel 2 from the wheel speed sensor 28.

Next, the slip ratio calculating means 103 calculates the slip ratio Sr of each wheel 2 from the radius R of the wheel 2, the rotational speed ω of the wheel 2, and the vehicle body speed V using the above formula (2) (S13).

Next, the braking / driving force control means 104b determines whether or not the slip ratio | Sr | of the largest wheel 2 among the slip ratios Sr of each wheel 2 exceeds the corresponding slip ratio upper limit values SrLimt-f and SrLimt-r. Judgment is made (S14).

For example, as shown in FIGS. 8 and 9, the slip ratio | Sr | of the front right wheel 2fr exceeds the corresponding slip ratio upper limit values SrLimt-f and SrLimt-r, and the slips of the other wheels 2fl, 2rr and 2rl When it is determined that the rate | Sr | does not exceed the corresponding slip upper limit values SrLimt-f and SrLimt-r (S4: Yes), the braking / driving force control means 104b detects the turning acceleration aθ detected by the acceleration sensor 26. It is equal to or exceeds the threshold A.theta. _t h a turn acceleration stored in the storage unit 110 (S15).

When the turning acceleration aθ exceeds the threshold value aθ _th (S15: Yes), the braking / driving force control unit 104b determines that the lateral acceleration aX detected by the acceleration sensor 26 is stored in the storage unit 110. It is determined whether or not the threshold value a _Xth is exceeded (S16).

When the turning acceleration aθ is equal to or less than the threshold value aθ _th (S15: No), the braking / driving force control means 104b performs control to bring the turning of the vehicle body 25 closer to the turning acceleration corresponding to the steering angle, as shown in FIG. (S17). That is, control is performed to reduce the braking / driving force of the front wheel motor 3f on the right wheel 2fr side where the slip ratio has increased, and control is performed to increase the braking / driving force of the rear wheel motor 3r. In this case, either one of the controls may be performed. By the above control, the turn is controlled to the turn intended by the driver, and the meandering of the vehicle body 25 can be suppressed.

Turn acceleration A.theta. Exceeds the threshold aθ _th (S15: Yes), and if the lateral acceleration a _X exceeds the threshold value a _Xth (S16: Yes), the braking-driving force control unit 104b is shown in FIG. 9 In this manner, control for suppressing the turning and lateral movement of the vehicle body 25 is performed (S18). That is, control is performed to reduce the braking / driving force of the front wheel motor 3f on the right wheel 2fr side where the slip ratio has increased, and control is performed to increase the braking / driving force of the rear wheel motor 3r. The ratio of increasing the braking / driving force of the rear wheel motor 3r is larger than that in the case of FIG. By the above control, turning and lateral movement are suppressed, and the meandering of the vehicle body 25 can be suppressed.

Turn acceleration A.theta. Exceeds the threshold aθ _th (S15: Yes), and if the lateral acceleration a _X does not exceed the threshold _{a Xth (S16: No),} S15: No similar, the braking-driving force control unit 104b As shown in FIG. 8, the vehicle body 25 is controlled to turn to turn acceleration corresponding to the steering angle (S17).

(Effect of the second embodiment)
According to the second embodiment, the following effects are obtained.
(A) Wheel lock and wheel spin, etc. that occur due to load movement caused by acceleration / deceleration, etc. can be suppressed, and transitional yaw rate and side slip, etc. that occur transiently depending on road surface conditions can be suppressed, realizing safe driving can do.
(B) Since movement of the vehicle is detected based on the slip ratio and acceleration, meandering can be detected more reliably.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, each means 101, 102, 103, 104a, 104b is realized by the CPU 100 and the braking / driving programs 113a, 113b, but may be realized by hardware such as ASIC (ApplicationＡSpecific IC).

The braking / driving programs 113a and 113b may be taken into the control device 10 from a computer-readable recording medium such as a CD-ROM in which the braking / driving programs 113b and 113b are recorded, or may be taken into the control device 10 from a server device or the like via a network. Good.

In addition to the above-described embodiments, the present invention provides an electric vehicle control device, an electric vehicle control method, and a computer-readable recording medium recording a braking / driving program according to the following other embodiments. You can also.

An electric vehicle control device according to another embodiment includes a first electric motor that transmits braking / driving force to the left and right wheels on the front wheel side via the first differential device, and a first electric motor on the left and right wheels on the rear wheel side. A device for controlling an electric vehicle including a second electric motor for transmitting braking / driving force via two differential devices, the first friction coefficient of the road surface on which the front wheel travels, and the rear wheel An estimation unit that estimates a second friction coefficient of a road surface on which the vehicle travels, a first predetermined value of a slip ratio of the front wheel according to the first friction coefficient, and the first friction coefficient according to the second friction coefficient A setting unit that sets a second predetermined value of the slip ratio of the rear wheel, a calculation unit that calculates the slip ratio of each wheel, and the higher slip ratio among the slip ratios of the left and right wheels on the front wheel side Controlling the braking / driving force of the first electric motor to be a first predetermined value, or And a control unit higher slip rate of the slip rate of the left and right wheels of the serial rear wheel to control the braking and driving force of the to be the second predetermined value a second electric motor.

An electric vehicle control method according to another embodiment includes a first electric motor for transmitting braking / driving force to the left and right wheels on the front wheel side via the first differential, and a first electric motor on the left and right wheels on the rear wheel side. A method for controlling an electric vehicle including a second electric motor that transmits braking / driving force via two differential devices, the first friction coefficient of the road surface on which the front wheel travels, and the rear wheel Estimating the second friction coefficient of the road surface on which the vehicle travels, the first predetermined value of the slip ratio of the front wheel according to the first friction coefficient, and the second friction coefficient according to the second friction coefficient A setting step for setting a second predetermined value of the slip ratio of the rear wheel, a calculation step for calculating the slip ratio of each wheel, and the higher slip ratio among the slip ratios of the left and right wheels on the front wheel side Controlling the first electric motor to a first predetermined value Control for controlling the force or the braking / driving force of the second electric motor so that the higher one of the slip ratios of the left and right wheels on the rear wheel side becomes the second predetermined value Steps.

A computer-readable recording medium according to another embodiment includes a first electric motor that transmits braking / driving force to the left and right wheels on the front wheel side via the first differential, and the left and right wheels on the rear wheel side. A computer included in an electric vehicle having a second electric motor that transmits braking / driving force via a second differential device has a first friction coefficient of a road surface on which the front wheels travel, and the rear wheels travel An estimation step of estimating a second friction coefficient of the road surface, a first predetermined value of a slip ratio of the front wheel according to the first friction coefficient, and the rear wheel according to the second friction coefficient A setting step for setting a second predetermined value of the slip ratio of the vehicle, a calculation step for calculating the slip ratio of each wheel, and the higher slip ratio of the slip ratios of the left and right wheels on the front wheel side is the first slip ratio. The first value so as to be a predetermined value of The braking / driving force of the second electric motor is controlled such that the braking / driving force of the pneumatic motor is controlled, or the higher slip ratio of the slip ratios of the left and right wheels on the rear wheel side becomes the second predetermined value. A program for executing a control step for controlling force is recorded.

It can be applied to automobiles having electric motors for driving front wheels and rear wheels, and hybrid cars having both electric motors and engines as power sources for wheels and capable of regenerative braking by electric motors. Regardless of type, such as lorry, ordinary car, large car, extra large car.

DESCRIPTION OF SYMBOLS 1 ... Electric vehicle, 2 ... Wheel, 2fr, 2fl ... Front wheel, 2rr, rl ... Rear wheel, 3f ... Motor for front wheel, 3r ... Motor for rear wheel, 4f ... Differential device for front wheel, 4r ... Differential for rear wheel Device, 5fr, 5fl, 5rr, 5rl ... axle, 7 ... power supply, 8f ... front wheel inverter, 8r ... rear wheel inverter, 9f ... front wheel drive circuit, 9r ... rear wheel drive circuit, 10 ... control device, DESCRIPTION OF SYMBOLS 11 ... Pressure adjustment unit, 12 ... Accelerator pedal, 13 ... Brake pedal, 14 ... Shift lever, 15a-15c ... Current sensor, 16f, 16r ... Encoder, 17a-17c ... Current sensor, 18fr, 18fl, 18rr, 18rl ... Machine Brake, 19 ... steering wheel, 20fr, 20fl ... camera, 21 ... camera, 22 ... accelerator sensor, 23 ... brake sensor, 24 ... shift sensor 25 ... Vehicle body, 26 ... Acceleration sensor, 27f, 27r ... Temperature sensor, 28 ... Wheel speed sensor, 29 ... Steering angle sensor, 70 ... Battery, 71f ... Smoothing capacitor for front wheel, 71r ... Smoothing capacitor for rear wheel, 72f, 72r ... voltage sensor, 73 ... battery capacity sensor, 100 ... CPU, 101 ... road surface friction coefficient μ estimation means, 102 ... slip ratio upper limit value setting means, 103 ... slip ratio calculation means, 104a, 104b ... braking / driving force control means, DESCRIPTION OF SYMBOLS 110 ... Memory | storage part, 111 ... Road surface pattern, 112 ... μ-SrLimit table, 113a, 113b ... Braking / driving program

Claims (14)

1. A first electric motor that transmits braking / driving force to the left and right wheels on the front wheel side via the first differential;
   A second electric motor for transmitting braking / driving force to the left and right wheels on the rear wheel side via a second differential;
   An estimation unit that estimates a first friction coefficient of a road surface on which the front wheels travel and a second friction coefficient of a road surface on which the rear wheels travel;
   A setting unit that sets a first predetermined value of the slip ratio of the front wheel in accordance with the first friction coefficient and a second predetermined value of the slip ratio of the rear wheel in accordance with the second friction coefficient. When,
   A calculation unit for calculating the slip ratio of each wheel;
   The braking / driving force of the first electric motor is controlled so that the higher one of the slip ratios of the left and right wheels on the front wheel side becomes the first predetermined value, or the left and right wheels on the rear wheel side are controlled. An electric vehicle comprising: a control unit configured to control a braking / driving force of the second electric motor so that a higher slip ratio of the wheel slip ratio becomes the second predetermined value.
2. The electric vehicle according to claim 1, wherein the control unit controls a braking / driving force of the first or second electric motor based on a load movement amount generated during driving or braking.
3. A friction brake mechanism capable of applying a braking force by friction to each of the wheels;
   The electric vehicle according to claim 1, wherein the control device controls the braking force of the mechanical brake mechanism when the braking force of the first or second electric motor is controlled.
4. 2. The electric vehicle according to claim 1, wherein the first and second predetermined values are slip rates at which a maximum braking / driving force can be obtained with the estimated friction coefficient.
5. The electric vehicle according to claim 3, wherein the control unit controls the braking / driving force and the braking force within a range not exceeding a braking / driving force by an operation of an accelerator or a brake.
6. When the calculated slip ratio of the front wheel or the rear wheel is equal to or less than the first or second predetermined value, the control unit performs the first or second operation according to an operation amount of an accelerator or a brake. Demonstrate the braking / driving force of the electric motor or the braking force of the friction brake mechanism,
   When the calculated slip of the front wheel or the rear wheel exceeds the first or second predetermined value, regardless of the operation amount of the accelerator or the brake, the first or second electric motor The electric vehicle according to claim 3, wherein control for reducing braking / driving force or braking force by the friction brake mechanism is performed.
7. When there is a difference in motor capacity between the first and second electric motors, the control unit determines the slip ratio of the left and right wheels having the larger motor capacity from the slip ratio of the left and right wheels having the smaller motor capacity. The electric vehicle according to claim 1, wherein the braking / driving force of the first and second electric motors is controlled with priority.
8. A steering angle detector for detecting the steering angle;
   The control unit includes the first and second control units within a range in which a slip rate of each wheel does not exceed the first and second predetermined values so that the turning acceleration becomes a turning acceleration corresponding to the steering angle. The electric vehicle according to claim 1, further comprising a controller that controls braking / driving force of the electric motor.
9. When the slip ratio of one of the rear wheels of each wheel exceeds a second predetermined value and the turning acceleration exceeds a predetermined acceleration against the steering angle, the control unit turns the turning Control that reduces the braking / driving force of the second electric motor so that the slip rate of one of the rear wheels is equal to or less than the second predetermined value so that the acceleration becomes a turning acceleration corresponding to the steering angle. And a control for increasing the braking / driving force of the first electric motor by an amount obtained by reducing the braking / driving force of the second electric motor within a range where the slip ratio of the front wheels does not exceed the first predetermined value. Item 9. The electric vehicle according to Item 8.
10. When the slip rate of one of the front wheels among the wheels exceeds a first predetermined value and the turning acceleration exceeds a predetermined acceleration against the steering angle, the turning acceleration is greater than the turning acceleration. Control for reducing the braking / driving force of the first electric motor so that the slip ratio of one of the front wheels is equal to or less than the first predetermined value so that the turning acceleration according to the steering angle becomes, The control is performed to increase the braking / driving force of the second electric motor by reducing the braking / driving force of the first electric motor within a range where the slip ratio of the rear wheel does not exceed the second predetermined value. 8. The electric vehicle according to 8.
11. The acceleration detection unit further detects lateral acceleration of the vehicle body,
    The control unit has a slip ratio of at least one of the wheels that exceeds the first and second predetermined values, and the turning acceleration and the lateral acceleration are different from the predetermined steering angle. The electric vehicle according to claim 10, wherein the braking / driving force of the first and second electric motors is controlled so that the turning acceleration becomes a turning acceleration corresponding to the steering angle when the acceleration exceeds a predetermined acceleration.
12. A first electric motor for transmitting braking / driving force to the left and right wheels on the front wheel side via the first differential device, and a braking / driving force to the left and right wheels on the rear wheel side via the second differential device. A computer included in an electric vehicle having a second electric motor;
    An estimation step for estimating a first friction coefficient of a road surface on which the front wheels travel and a second friction coefficient of a road surface on which the rear wheels travel;
    A setting step of setting a first predetermined value of the slip ratio of the front wheel according to the first friction coefficient and a second predetermined value of the slip ratio of the rear wheel according to the second friction coefficient. When,
    A calculation step for calculating the slip ratio of each wheel;
    The braking / driving force of the first electric motor is controlled so that the higher one of the slip ratios of the left and right wheels on the front wheel side becomes the first predetermined value, or the left and right wheels on the rear wheel side are controlled. A program for executing a control step of controlling a braking / driving force of the second electric motor so that a higher slip ratio of the wheel slip ratio becomes the second predetermined value.
13. A first electric motor that transmits braking / driving force to the left and right wheels on the front wheel side via the first differential;
    A device for controlling an electric vehicle including a second electric motor that transmits braking / driving force to the left and right wheels on the rear wheel side via a second differential device;
    An estimation unit that estimates a first friction coefficient of a road surface on which the front wheels travel and a second friction coefficient of a road surface on which the rear wheels travel;
    A setting unit that sets a first predetermined value of the slip ratio of the front wheel in accordance with the first friction coefficient and a second predetermined value of the slip ratio of the rear wheel in accordance with the second friction coefficient. When,
    A calculation unit for calculating the slip ratio of each wheel;
    The braking / driving force of the first electric motor is controlled so that the higher one of the slip ratios of the left and right wheels on the front wheel side becomes the first predetermined value, or the left and right wheels on the rear wheel side are controlled. A control device for an electric vehicle, comprising: a controller that controls a braking / driving force of the second electric motor so that a higher slip ratio of the slip ratio of the wheel becomes the second predetermined value.
14. A first electric motor that transmits braking / driving force to the left and right wheels on the front wheel side via the first differential;
    A method of controlling an electric vehicle including a second electric motor that transmits braking / driving force to the left and right wheels on the rear wheel side via a second differential device,
    An estimation step for estimating a first friction coefficient of a road surface on which the front wheels travel and a second friction coefficient of a road surface on which the rear wheels travel;
    A setting step of setting a first predetermined value of the slip ratio of the front wheel according to the first friction coefficient and a second predetermined value of the slip ratio of the rear wheel according to the second friction coefficient. When,
    A calculation step for calculating the slip ratio of each wheel;
    The braking / driving force of the first electric motor is controlled so that the higher one of the slip ratios of the left and right wheels on the front wheel side becomes the first predetermined value, or the left and right wheels on the rear wheel side are controlled. A control step of controlling a braking / driving force of the second electric motor so that a higher slip ratio of the wheel slip ratio becomes the second predetermined value.

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