Electric vehicle control method and electric vehicle control device

Abstract

One embodiment of the present invention is an electric vehicle control method in which braking torque is generated by using regenerative torque by an electric motor and friction torque by a friction brake. In this control method, when slip of a wheel is detected in a situation where the braking torque is generated by using both the regenerative torque and the friction torque, the friction torque is maintained at the value at the time when the slip of the wheel is detected, and the regenerative torque is adjusted.

Description

Control method for electric vehicles, and control device for electric vehicles

[0001] The present invention relates to a control method and control device for electric vehicles.

[0002] JP2003-320929A discloses a braking control device that generates braking force in an electric vehicle by coordinating the control of a motor generator and a mechanical brake. In particular, in this braking control device, the distribution of regenerative control torque generated by the motor generator and friction braking torque (fluid pressure braking torque) generated by the mechanical brake is adjusted according to the slip ratio.

[0003] Electric vehicles may be equipped with a so-called regenerative braking system. A regenerative braking system is a braking system that coordinates the control of friction brakes with the control of regenerative brakes using an electric motor. In other words, when a regenerative braking system is in operation, an electric vehicle generates braking torque using the regenerative torque from the electric motor and the friction torque from the friction brakes.

[0004] Electric vehicles are also typically equipped with a braking system called an anti-lock braking system or anti-skid braking system (hereinafter referred to as ABS). ABS is a braking system that suppresses slip (skid) by controlling friction brakes. However, friction brakes have a response delay in the hydraulic pressure that operates them. For this reason, vibrations are likely to occur in the vehicle body when the ABS is activated.

[0005] Furthermore, in situations where regenerative braking and friction braking are used in combination, if slip is detected, ABS usually takes priority. That is, if slip is detected while braking with regenerative braking, the braking system switches from regenerative braking to ABS. As a result, electric vehicles turn off regenerative braking and use friction brakes alone to suppress slip. This can easily cause vibrations in the vehicle body.

[0006] However, in situations where regenerative braking is in operation, electric vehicles are already controlling both regenerative and friction brakes. Therefore, rather than switching the braking system to a conventional ABS that uses only friction brakes, it is desirable for electric vehicles to achieve both slip suppression and body vibration suppression through the control of regenerative braking.

[0007] The present invention aims to provide a control method for electric vehicles that achieves both slip suppression and vehicle body vibration suppression through the control of regenerative cooperative braking, and a control device for electric vehicles.

[0008] One aspect of the present invention is a control method for an electric vehicle that generates braking torque using regenerative torque from an electric motor and friction torque from a friction brake. In this control method, when wheel slip is detected in a situation where braking torque is generated using both regenerative torque and friction torque, the friction torque is maintained at the value at the time the wheel slip was detected, and the regenerative torque is adjusted.

[0009] Figure 1 is an explanatory diagram showing the schematic configuration of an electric vehicle. Figure 2 is a block diagram showing the configuration of the controller. Figure 3 is a flowchart related to the braking control of an electric vehicle. Figure 4 is a schematic graph showing the changes in motor torque command, friction torque command, and wheel torque, etc., for the braking control of the first comparative example. Figure 5 is a schematic graph showing the changes in motor torque command, friction torque command, and wheel torque, etc., for the braking control of this embodiment. Figure 6 is a schematic graph showing the changes in motor torque command, friction torque command, and wheel torque, etc., when slip is detected in the second comparative example before the braking force corresponding to the friction torque is actually generated. Figure 7 is a schematic graph showing the changes in motor torque command, friction torque command, and wheel torque, etc., when slip is detected in the braking control of this embodiment before the braking force corresponding to the friction torque is actually generated. Figure 8 is a schematic graph showing the changes in the motor torque command, friction torque command, and wheel torque, etc., when the torque command set according to the slip ratio becomes minimal in the braking control of this embodiment.

[0010] Embodiments of the present invention will be described below with reference to the drawings.

[0011] Figure 1 is an explanatory diagram showing the schematic configuration of an electric vehicle 100. The electric vehicle 100 is a vehicle that generates all or part of its driving force using an electric motor 15, and is, for example, an electric vehicle or a hybrid vehicle. As shown in Figure 1, the electric vehicle 100 includes an electric powertrain 10, a friction brake 11, and a controller 12.

[0012] The electric powertrain 10 is a braking and driving system that generates driving and braking forces for the electric vehicle 100 using an electric motor 15. In this embodiment, the electric powertrain 10 includes a power generation system that generates electricity to operate the electric vehicle 100, in addition to the braking and driving system. That is, the electric vehicle 100 in this embodiment is a so-called series hybrid vehicle. As shown in Figure 1, the braking and driving system consists of a battery 13, an inverter 14, and an electric motor 15, etc. The power generation system consists of an engine 16 and a generator 17, etc.

[0013] The battery 13 is a DC power source that stores power supplied to various parts of the electric vehicle 100, such as the electric motor 15. The battery 13 is rechargeable. In this embodiment, the battery 13 is charged by power generated by the generator 17 (generated power) or power generated by the electric motor 15 through regenerative control (regenerative power). The battery 13 is made of, for example, a lithium-ion battery. Parameters representing the state of the battery 13, such as State of Charge (SOC) representing the amount of charge, are measured or calculated as needed.

[0014] The inverter 14 converts the DC power output by the battery 13 into AC power and supplies it to the motor 15. When the motor 15 generates regenerative power, the inverter 14 converts the AC regenerative power into DC power and supplies it to the battery 13. Also, when the power generation system is operating, the inverter 14 converts the generated power input from the generator 17 into DC power and supplies it to the battery 13.

[0015] The electric motor 15 is a rotating electric machine that functions as both a drive source and a braking source for the electric vehicle 100. The electric motor 15 is, for example, a three-phase AC synchronous motor. The output shaft of the electric motor 15 is connected to all or some of the four wheels 18 via a reduction gear, gears, and a drive shaft, etc.

[0016] Specifically, the electric motor 15 rotates using power supplied from the battery 13, thereby generating torque (hereinafter referred to as electric motor torque T) on its output shaft. ｍ This produces the motor torque T. ｍ This is transmitted to the wheels 18 via the drive shaft, etc., generating driving force in the electric vehicle 100. Below, the motor torque T when the electric motor 15 generates driving force in the electric vehicle 100 is described. ｍ This is sometimes specifically referred to as driving torque. In this embodiment, for simplicity, the electric vehicle 100 is assumed to move forward, T ｍ When > 0, the motor torque T ｍ This represents the driving torque.

[0017] When the electric motor 15 rotates in conjunction with the wheels 18, it generates regenerative power using the kinetic energy of the electric vehicle 100. At this time, regenerative braking force is generated in the electric vehicle 100. Hereinafter, the control that generates regenerative power and regenerative braking force by the electric motor 15 will be referred to as regenerative control. In contrast to braking by the friction brake 11, the braking mode of the electric vehicle 100 in which the electric motor 15 generates regenerative braking force will be referred to as regenerative braking. The electric motor torque T during regenerative control will be... ｍ This is sometimes specifically referred to as regenerative torque. In this embodiment, as described above, the electric vehicle 100 moves forward. Therefore, T ｍ When < 0, the motor torque T ｍ This becomes regenerative torque.

[0018] Engine 16 is an internal combustion engine that constitutes a power generation system, and its output shaft is connected to generator 17. Engine 16 rotates using gasoline or other fuel and generates power on the output shaft. That is, engine 16 rotates generator 17. Thereby, the power generation system generates electricity. Engine 16 is operated as appropriate as needed based on the SOC of battery 13, etc.

[0019] Generator 17 rotates by engine 16 and generates AC power. Generator 17 is constituted by, for example, a three-phase AC synchronous generator. When it is necessary to discharge battery 13, that is, when it is necessary to actively consume the power of battery 13, generator 17 receives power supply from battery 13 via inverter 14 and is rotated by power running. In this case, engine 16 idles by generator 17. In the present embodiment, when the SOC is in a high state such that sufficient regenerative power cannot be received and the regenerative braking force (regenerative torque) is limited, battery 13 is discharged by the idling of engine 16. The discharge control of battery 13 using engine 16 of the power generation system is called motoring.

[0020] Friction brake 11 is a braking source that generates a braking force on electric vehicle 100 by the frictional force applied to wheels 18. Friction brake 11 generally operates by the operation of the brake pedal by the driver. Hereinafter, the braking torque generated by friction brake 11 is referred to as friction torque T Ｂ as described above. In the present embodiment, as described above, it is assumed that electric vehicle 100 moves forward. For this reason, friction torque T Ｂ is a negative value (T Ｂ < 0).

[0021] In electric vehicle 100, friction brake 11 may be controlled by controller 12. In the present embodiment, particularly, when the regenerative brake (regenerative torque) is insufficient with respect to the braking force required for electric vehicle 100, friction brake 11 is used additionally to compensate for the deficiency. That is, electric vehicle 100 is equipped with a regenerative cooperative braking system, and as needed, the regenerative torque (T ｍ<0) and friction torque T due to friction brake 11 Ｂ Both are used to generate braking torque (braking force).

[0022] The controller 12 is a control device that comprehensively controls each part of the electric vehicle 100. The controller 12 is composed of, for example, one or more computers and is programmed to control each part of the electric vehicle 100 at a predetermined control cycle.

[0023] Figure 2 is a block diagram showing the configuration of the controller 12. Here, the configuration of the controller 12 mainly shows the components related to braking control of the electric vehicle 100 by regenerative cooperative braking. As shown in Figure 2, the controller 12 includes a request torque calculation unit 21, a slip ratio calculation unit 22, a limited regenerative torque calculation unit 23, a regenerative power calculation unit 24, a discharge power calculation unit 25, a maximum regenerative torque calculation unit 26, a motor torque calculation unit 27, a motor control unit 28, a friction torque calculation unit 29, and a friction brake control unit 30.

[0024] The required torque calculation unit 21 calculates the accelerator operation amount A ｐｏ Based on the vehicle speed V, the required torque T ｒｅｑ The following is calculated: Accelerator input amount A ｐｏ This parameter represents the amount of accelerator pedal operation by the driver and is acquired as needed. The vehicle speed V is, for example, the rotational speed N of the electric motor 15. ｍ The required torque T is measured as appropriate based on (not shown in the diagram). ｒｅｑ This parameter represents the torque that the driver requests from the electric vehicle 100 through the operation of the accelerator pedal, etc. When the driver presses the accelerator pedal further, the requested torque T ｒｅｑ This represents the driving torque that accelerates the electric vehicle 100. On the other hand, if the driver reduces the pressure on the accelerator pedal, the required torque T ｒｅｑ This represents the braking torque that slows down the electric vehicle 100.

[0025] In this embodiment, the required torque calculation unit 21 calculates the accelerator operation amount A ｐｏ And the vehicle speed V and the required torque T ｒｅｑIt has a torque map that has been pre-associated with the accelerator operation amount A through experimentation or simulation. Therefore, the required torque calculation unit 21 refers to this torque map to calculate the accelerator operation amount A ｐｏ and the required torque T according to the vehicle speed V. ｒｅｑ Perform the calculation.

[0026] The slip ratio calculation unit 22 calculates the vehicle speed V (vehicle speed) and the wheel speed v ｗ The slip ratio SR [%] is calculated using this. The slip ratio calculation unit 22 then detects the presence and degree of slip (skid) of the wheel 18. In this embodiment, the slip ratio SR is set to a threshold Th predetermined by experiment or simulation. ＳＲ When the slip ratio calculation unit 22 becomes greater than (not shown), it determines that slip has occurred in the wheel 18. The slip ratio calculation unit 22 determines, for example, the rotational speed N of the wheel 18. ｗ Wheel speed v using [rpm] ｗ The slip ratio SR can be calculated as SR = (V - v ｗ It is calculated by ) / V.

[0027] The slip ratio calculation unit 22 calculates the slip ratio SR for each wheel 18. However, in this embodiment, for simplicity, the slip ratio SR of each wheel 18 is not distinguished and is represented by a single parameter. Therefore, in this embodiment, the slip ratio SR is, for example, the maximum value of the slip ratio SR calculated for each wheel 18.

[0028] Note that the slip ratio SR is an example of a parameter used to determine the presence and degree of slip (skid) of the wheels 18. The electric vehicle 100 uses the wheel speed v of each wheel 18 instead of the slip ratio SR. ｗ Deviations in rotational speed, etc., can be used as parameters for determining slip (skid).

[0029] The limited regenerative torque calculation unit 23 calculates the limited regenerative torque T ｒｇ－ｌｉｍ Calculate the limited regenerative torque T. ｒｇ－ｌｉｍThis is a limit value (upper limit) for the magnitude of the regenerative torque, and is set according to the degree of slip. In this embodiment, the limit regenerative torque calculation unit 23 calculates the limit regenerative torque T according to the slip ratio SR. ｒｇ－ｌｉｍ Specifically, the limiting regenerative torque calculation unit 23 uses feedback control to set the limiting regenerative torque T such that the slip ratio SR matches or approaches zero. ｒｇ－ｌｉｍ Set or change the following. Therefore, as a general rule, the larger the slip ratio SR, the greater the limited regenerative torque T. ｒｇ－ｌｉｍ It becomes smaller, and its value approaches zero. On the other hand, the smaller the slip ratio SR becomes, the limiting regenerative torque T ｒｇ－ｌｉｍ It increases, and its value moves away from zero. Note that the limited regenerative torque T ｒｇ－ｌｉｍ This is when the slip ratio SR is zero, at least the maximum regenerative torque T described later. ｒｇ－ｍａｘ The settings will be configured to achieve the above values.

[0030] The regenerative power calculation unit 24 calculates the regenerative power P based on the State of Control (SOC) of the battery 13. １ The regenerative power P is calculated. １ This parameter represents the regenerative power that the battery 13 can accept. Since the electric motor 15 cannot generate regenerative power exceeding the amount that the battery 13 can accept, regenerative braking (regenerative braking force) is limited by this regenerative power P. １ It is restricted by.

[0031] The discharge power calculation unit 25 calculates the rotational speed N of the generator 17 when the engine 16 is running idle. ｇ and Torque T ｇ Based on this, discharge power P ２ Calculate the discharge power P. ２ This parameter represents the power of the battery 13 that can be discharged (consumed) using the power generation system. More simply, it represents the discharge power P. ２ This represents the power that can be consumed by running the engine 16 idle. Also, the discharge power P ２ P is regenerative power １ This is a parameter that corrects the rotational speed N of the generator 17. ｇ and Torque T ｇThis parameter is acquired as needed to represent the state of the power generation system.

[0032] The maximum regenerative torque calculation unit 26 calculates the regenerative power P １ , or regenerative power P １ and discharge power P ２ Based on this, maximum regenerative torque T ｒｇ－ｍａｘ Calculate the maximum regenerative torque T. ｒｇ－ｍａｘ This parameter represents the maximum regenerative torque that can be generated by the electric motor 15 (the maximum value of the regenerative torque).

[0033] The maximum regenerative torque calculation unit 26, in principle, calculates the regenerative power P １ Based on this, maximum regenerative torque T ｒｇ－ｍａｘ The calculation is performed. However, in the power generation system, when the state of charge of the battery 13 is reduced by running the engine 16 idle, the maximum regenerative torque calculation unit 26 calculates the regenerative power P １ and discharge power P ２ Based on the sum of the maximum regenerative torque T ｒｇ－ｍａｘ Perform the calculation.

[0034] Regenerative power P １ (or regenerative power P) １ and discharge power P ２ The larger the sum of T, the greater the maximum regenerative torque. ｒｇ－ｍａｘ It gets larger and moves away from zero. Meanwhile, the regenerative power P １ (or regenerative power P) １ The larger the sum of the discharge power P2, the greater the maximum regenerative torque T. ｒｇ－ｍａｘ It becomes smaller and approaches zero.

[0035] The motor torque calculation unit 27 calculates the required torque T ｒｅｑ , limited regenerative torque T ｒｇ－ｌｉｍ , and maximum regenerative torque T ｒｇ－ｍａｘ Based on the motor torque command T ｍ ＊ The motor torque command T is calculated. ｍ ＊ The motor torque T ｍ This is a directive regarding this matter.

[0036] Specifically, the motor torque calculation unit 27 generally sets the required torque T ｒｅｑ as the motor torque command T ｍ ＊ . In particular, when the required torque T ｒｅｑ is a positive value (driving torque), the motor torque calculation unit 27 sets the required torque T ｒｅｑ as the motor torque command T ｍ ＊ .

[0037] On the other hand, when the required torque T ｒｅｑ is a negative value (regenerative torque), the motor torque calculation unit 27 sets the motor torque command T ｍ ＊ as follows.

[0038] First, when the required torque T ｒｅｑ is equal to or less than the maximum regenerative torque T ｒｇ－ｍａｘ or the limited regenerative torque T ｒｇ－ｌｉｍ , the motor torque calculation unit 27 sets the motor torque command T ｍ ＊ to the required torque T ｒｅｑ .

[0039] Next, when the required torque T ｒｅｑ is greater than the maximum regenerative torque T ｒｇ－ｍａｘ or the limited regenerative torque T ｒｇ－ｌｉｍ , the motor torque calculation unit 27 sets the motor torque command T ｍ ＊ to a value equal to or less than the maximum regenerative torque T ｒｇ－ｍａｘ or the limited regenerative torque T ｒｇ－ｌｉｍ .

[0040] In this embodiment, the motor torque calculation unit 27 presets the minimum braking torque T ｍｉｎ for the braking torque. The minimum braking torque T ｍｉｎ defines the minimum braking torque (the minimum required braking torque) generated when the regenerative torque, or the regenerative torque and the frictional torque, generate the braking torque. The minimum braking torque T ｍｉｎ is determined in advance based on experiments or simulations. The minimum braking torque T ｍｉｎ is a negative value (T ｍｉｎ < 0).

[0041] And, maximum regenerative torque T ｒｇ－ｍａｘ The minimum braking torque T ｍｉｎ When the above is true (T ｒｇ－ｍａｘ ≧T ｍｉｎ The motor torque calculation unit 27 calculates the motor torque command T ｍ ＊ Minimum braking torque T ｍｉｎ Set to the maximum regenerative torque T. ｒｇ－ｍａｘ The minimum braking torque T ｍｉｎ When it is smaller than (T ｍｉｎ >T ｒｇ－ｍａｘ The motor torque calculation unit 27 calculates the motor torque command T ｍ ＊ Maximum regenerative torque T ｒｇ－ｍａｘ Set to this.

[0042] Furthermore, slippage occurs in the wheel 18, and the maximum regenerative torque T ｒｇ－ｍａｘ Smaller limited regenerative torque T ｒｇ－ｌｉｍ When this is set (T ｒｇ－ｍａｘ >T ｒｇ－ｌｉｍ The motor torque calculation unit 27 calculates the maximum regenerative torque T ｒｇ－ｍａｘ Instead, a limited regenerative torque T ｒｇ－ｌｉｍ Motor torque command T ｍ ＊ Set to this.

[0043] In other words, the limited regenerative torque T ｒｇ－ｌｉｍ The minimum braking torque T ｍｉｎ When the above is true (T ｒｇ－ｌｉｍ ≧T ｍｉｎ The motor torque calculation unit 27 calculates the motor torque command T ｍ ＊ Minimum braking torque T ｍｉｎ Set to this. Meanwhile, the limited regenerative torque T ｒｇ－ｌｉｍ The minimum braking torque T ｍｉｎ When it is smaller than (T ｍｉｎ >T ｒｇ－ｌｉｍ The motor torque calculation unit 27 calculates the motor torque command T ｍ ＊ Regenerative torque limiting T ｒｇ－ｌｉｍ Set to this.

[0044] Thus, the required torque T ｒｅｑIf the value is negative (regenerative torque), the motor torque calculation unit 27 calculates the required torque T. ｒｅｑ Maximum regenerative torque T ｒｇ－ｍａｘ or limited regenerative torque T ｒｇ－ｌｉｍ The value is limited to the smaller of the two. However, as mentioned above, the limited regenerative torque T ｒｇ－ｌｉｍ This changes according to the slip ratio SR. As a result, slip occurs in the wheel 18, and the motor torque command T ｍ ＊ Regenerative torque limit ｒｇ－ｌｉｍ In the situation where this is set, the motor torque calculation unit 27 substantially calculates the motor torque command T according to the slip ratio SR. ｍ ＊ This changes the slip ratio SR. Therefore, the regenerative torque actually generated by the electric motor 15 fluctuates according to the slip ratio SR so that the slip ratio SR is reduced. In other words, when slip occurs in the wheel 18, the electric motor torque calculation unit 27 adjusts the regenerative torque according to the slip ratio SR so that the slip is eliminated.

[0045] The motor control unit 28 issues a motor torque command T ｍ ＊ Based on this, the motor 15 is controlled. Specifically, the motor control unit 28 controls the motor torque command T ｍ ＊ The inverter 14 is switched accordingly. As a result, the motor 15 receives the motor torque command T ｍ ＊ Motor torque T corresponding to ｍ Outputs.

[0046] The friction torque calculation unit 29 calculates the required torque T ｒｅｑ Maximum regenerative torque T ｒｇ－ｍａｘ , slip ratio SR, and limited regenerative torque T ｒｇ－ｌｉｍ Based on the friction torque command T Ｂ ＊ Calculate (set) it.

[0047] Specifically, the friction torque command T Ｂ ＊ In principle, the required torque T ｒｅｑ Maximum regenerative torque T ｒｇ－ｍａｘ Larger than (T ｒｅｑ >Tｒｇ－ｍａｘ ), required torque T ｒｅｑ When regenerative torque is insufficient, it is set to compensate for at least a portion of that deficiency.

[0048] In this embodiment, insufficient regenerative torque is reduced to the minimum braking torque T ｍｉｎ It is compensated up to T. Therefore, in this embodiment, ｍｉｎ >T ｒｇ－ｍａｘ In this case, the friction torque calculation unit 29 determines T Ｂ ＊ = T ｍｉｎ -T ｒｇ－ｍａｘ The friction torque command T is set to be such that Ｂ ＊ Set the maximum regenerative torque T. ｒｇ－ｍａｘ The minimum braking torque T ｍｉｎ That is all (T ｒｇ－ｍａｘ ≧T ｍｉｎ ), minimum braking torque T ｍｉｎ When the entire minimum braking torque corresponding to can be achieved by regenerative torque, the friction torque calculation unit 29 calculates the friction torque command T Ｂ ＊ Set it to zero.

[0049] Then, slip occurs in wheel 18, and the maximum regenerative torque T ｒｇ－ｍａｘ Smaller limited regenerative torque T ｒｇ－ｌｉｍ When this is set (T ｒｇ－ｍａｘ >T ｒｇ－ｌｉｍ The friction torque calculation unit 29 will issue a friction torque command T until the slip is eliminated. Ｂ ＊ Maintain the value at the time slip occurs. That is, the slip ratio SR is the threshold Th ＳＲ As the slippage of the wheel 18 increases, a friction torque command T is issued. Ｂ ＊ It does not fluctuate and remains at a constant value.

[0050] However, friction torque command T Ｂ ＊ After setting the friction torque T is actually applied by the friction brake 11. Ｂ If slippage of the wheel 18 is detected before it occurs, the friction torque calculation unit 29 will, exceptionally, issue a friction torque command TＢ ＊ Set it to zero. That is, friction torque command T Ｂ ＊ (=T ｍｉｎ -T ｒｇ－ｍａｘ After setting the friction torque T Ｂ If the wheel 18 slips before the slip occurs, the friction torque calculation unit 29 sets the friction torque command T at the time the slip was detected. Ｂ ＊ Discard it and reset it to zero.

[0051] The friction torque calculation unit 29 calculates, for example, the friction torque T actually generated by the friction brake 11. Ｂ This can be detected as needed using sensors or other devices not shown in the diagram.

[0052] Furthermore, if slippage occurs in the wheel 18, the regenerative torque will be limited to the regenerative torque T. ｒｇ－ｌｉｍ In situations where the torque is limited, the regenerative torque limit T corresponds to the slip ratio SR. ｒｇ－ｌｉｍ When it is determined that the friction torque is extremely small, the friction torque calculation unit 29 exceptionally issues the friction torque command T Ｂ ＊ Set to zero. In this embodiment, the limited regenerative torque T ｒｇ－ｌｉｍ When the friction torque becomes almost zero, the friction torque calculation unit 29 calculates the friction torque command T at the time slip was detected. Ｂ ＊ (=T ｍｉｎ -T ｒｇ－ｍａｘ Discard the value and reset it to zero.

[0053] In this embodiment, the friction torque calculation unit 29 calculates the limited regenerative torque T ｒｇ－ｌｉｍ For example, when it is less than or equal to a predetermined reference value ε based on experiments or simulations, the limited regenerative torque T ｒｇ－ｌｉｍ We determine that it is approximately equal to zero. That is, T ｒｇ－ｌｉｍ If ≤ε, the friction torque calculation unit 29 calculates T Ｂ ＊ Set to =0.

[0054] The friction brake control unit 30 receives the friction torque command T Ｂ ＊Accordingly, the friction brake 11 is controlled. As a result, the friction brake 11 controls the minimum braking torque T ｍｉｎ It automatically activates when the regenerative torque is insufficient. The friction brake 11 then receives the friction torque command T Ｂ ＊ Friction torque T corresponding to Ｂ By generating this, even when the driver is not operating the brake pedal, the minimum braking torque (minimum braking torque T) is applied in coordination with the regenerative braking by the electric motor 15. ｍｉｎ This causes ) to occur.

[0055] Figure 3 is a flowchart relating to braking control in the electric vehicle 100. Here, we will explain the braking control when braking the electric vehicle 100 using regenerative braking. Also, for simplicity, we will use as an example a scenario in which the electric vehicle 100 is decelerated while the driver is not pressing either the accelerator pedal or the brake pedal. That is, here, accelerator operation amount A ｐｏ Assume that the value is zero and the brake pedal is not pressed.

[0056] As shown in Figure 3, in step S10, the requested torque calculation unit 21 calculates the requested torque T ｒｅｑ The maximum regenerative torque calculation unit 26 calculates the maximum regenerative torque T ｒｇ－ｍａｘ The motor torque calculation unit 27 calculates the required torque T. ｒｅｑ and maximum regenerative torque T ｒｇ－ｍａｘ Compare them.

[0057] In step S11, the maximum regenerative torque T ｒｇ－ｍａｘ The required torque T ｒｅｑ If it is smaller than (T ｒｇ－ｍａｘ <T ｍｉｎ The control then proceeds to step S12. In step S12, the controller 12 starts the engine 16 idle in the power generation system, consuming power from the battery 13. Therefore, the discharge power P generated by the start of this discharge control is ２ By that amount, maximum regenerative torque T ｒｇ－ｍａｘ (Effective regenerative power P) １) increases. Then, in step S13, the maximum regenerative torque calculation unit 26 calculates the discharge power P ２ Including the maximum regenerative torque T ｒｇ－ｍａｘ The motor torque calculation unit 27 calculates this and sets it to the minimum braking torque T ｍｉｎ Compare it to this.

[0058] On the other hand, in step S11, the maximum regenerative torque T ｒｇ－ｍａｘ However, the required torque T ｒｅｑ If the above (T ｒｇ－ｍａｘ ≧T ｍｉｎ ), skip step S12 and proceed to step S13. In this case, the motor torque calculation unit 27 calculates the regenerative power P １ Maximum regenerative torque T based on ｒｇ－ｍａｘ Minimum braking torque T ｍｉｎ Compare it to this.

[0059] In step S13, the maximum regenerative torque T ｒｇ－ｍａｘ The minimum braking torque T ｍｉｎ If it is greater than or equal to, the control proceeds to step S14. In step S14, the motor torque calculation unit 27 calculates the motor torque command T ｍ ＊ Minimum braking torque T ｍｉｎ The setting is configured as follows: As a result, the electric vehicle 100 achieves a minimum braking torque T through regenerative braking. ｍｉｎ It generates the minimum braking force necessary to slow down.

[0060] In step S13, the maximum regenerative torque T ｒｇ－ｍａｘ The minimum braking torque T ｍｉｎ If the following conditions are met, the control proceeds to step S15. In step S15, the friction torque calculation unit 29 issues the friction torque command T Ｂ ＊ This calculates the minimum braking torque T. ｍｉｎ To compensate for the insufficient regenerative torque, the friction torque command T Ｂ ＊ Set the friction torque command T. Ｂ ＊ is, T Ｂ ＊ = T ｍｉｎ -T ｒｇ－ｍａｘ It is set to the value calculated by [the relevant method].

[0061] Subsequently, in step S16, the electric vehicle 100 uses both regenerative braking and friction braking 11 to achieve a minimum braking torque T ｍｉｎ The motor decelerates with the minimum braking force corresponding to the motor torque command T. Specifically, the motor control unit 28 controls the motor torque command T. ｍ ＊ Maximum regenerative torque T ｒｇ－ｍａｘ The motor 15 is driven by setting it to this value. The friction brake control unit 30 also sets the friction torque command T Ｂ ＊ The friction brake 11 is driven accordingly. As a result, the overall braking torque is the minimum braking torque T ｍｉｎ Therefore, as described above, the electric vehicle 100 has a minimum braking torque T ｍｉｎ It generates the minimum braking force corresponding to the situation, causing deceleration.

[0062] In step S17, the slip ratio calculation unit 22 monitors the slip of the wheel 18 by calculating the slip ratio SR. In step S17, when the slip ratio SR is threshold Th ＳＲ When the amount of slippage becomes greater and wheel slippage of the 18 is detected, the control proceeds to step S18.

[0063] In step S18, the limited regenerative torque calculation unit 23 calculates the limited regenerative torque T according to the slip ratio SR. ｒｇ－ｌｉｍ The motor control unit 28 calculates the motor torque command T. ｍ ＊ Regenerative torque limiting T ｒｇ－ｌｉｍ The motor 15 is driven by setting it to this value. Therefore, the regenerative torque is effectively limited to the regenerative torque T. ｒｇ－ｌｉｍ It is set to and adjusted according to the slip ratio SR.

[0064] In step S19, the friction torque calculation unit 29 calculates the actual friction torque T by the friction brake 11. Ｂ Check whether or not friction torque T is occurring. In step S19, the friction torque T is still present. Ｂ If it is determined that no friction torque has occurred, the process proceeds to step S20, and the friction torque calculation unit 29 issues the friction torque command T Ｂ ＊Reset to zero. Meanwhile, in step S19, friction torque command T Ｂ ＊ When it is determined that a corresponding friction torque TB is actually being generated, the control proceeds to step S21.

[0065] In step S21, the friction torque calculation unit 29 calculates the limited regenerative torque T ｒｇ－ｌｉｍ The regenerative torque T is compared with a predetermined reference value ε. In step S21, the limited regenerative torque T ｒｇ－ｌｉｍ (T ｒｇ－ｌｉｍ ≤ε), Regenerative torque T ｒｇ－ｌｉｍ When it is small enough to be considered practically zero, the process proceeds to step S20. That is, the friction torque calculation unit 29 calculates the friction torque command T Ｂ ＊ Reset to zero. Meanwhile, in step S21, the limited regenerative torque T ｒｇ－ｌｉｍ When (T ｒｇ－ｌｉｍ >ε), proceeding to step S22, the friction torque calculation unit 29 sets the friction torque command T set at the time slip is detected. Ｂ ＊ Maintain.

[0066] In other words, when the electric vehicle 100 is decelerating by regenerative cooperative braking, if slippage of the wheel 18 is detected, the regenerative torque is limited to the regenerative torque T. ｒｇ－ｌｉｍ It is set to and adjusted according to the slip ratio SR. On the other hand, the friction torque T Ｂ In principle, the value is maintained at the set value when slip is detected. However, the friction torque command T Ｂ ＊ After it is set, the actual friction torque T Ｂ If slip is detected before the slip occurs (S19: NO), or if the regenerative torque is adjusted according to the slip ratio SR (limited regenerative torque T) ｒｇ－ｌｉｍ If the value becomes extremely small (S21: NO), exceptionally, the friction torque command T set at the time slip was detected will be applied. Ｂ ＊ It is discarded, friction torque command T Ｂ ＊ It is reset to zero.

[0067] Thus, in the braking control of this embodiment, when wheel slip is detected while decelerating by regenerative cooperative braking, the electric vehicle 100 applies friction torque T Ｂ While maintaining this state, slippage is eliminated by adjusting the regenerative torque.

[0068] Figure 4 shows the braking control of the first comparative example, with respect to the motor torque command T. ｍ ＊ , friction torque command T Ｂ ＊ , and wheel torque T ｗ This graph schematically shows the changes in these factors. The first comparative example is an example in which, when wheel slip is detected while decelerating by regenerative cooperative braking, the regenerative braking is turned off and the slip is eliminated by a conventional ABS that controls only the friction brake 11.

[0069] Figure 4(A) shows accelerator pedal operation amount A. ｐｏ This is a graph showing the changes in the vehicle speed V. Figure 4(B) is a graph showing the changes in the motor torque command T. ｍ ＊ This graph shows the trend. Figure 4(C) shows the maximum regenerative torque T. ｒｇ－ｍａｘ This is indicated by a dashed line. Also, the maximum regenerative torque T ｒｇ－ｍａｘ or limited regenerative torque T ｒｇ－ｌｉｍ Motor torque command T when not subject to the restrictions ｍ ＊ (i.e., the required torque T) ｒｅｑ ) is shown with a dashed line. Also, the minimum braking torque T due to regenerative braking. ｍｉｎ The level is indicated by a dotted line. Figure 4(D) shows the rotational speed N of the generator 17. ｇ This is a graph showing the trend of [the following]. Figure 4(E) is a graph showing the trend of the slip ratio SR. Figure 4(F) shows the friction torque command T Ｂ ＊ This is a graph showing the trend. In Figure 4(F), in a conventional ABS that eliminates slip by controlling the friction brake 11, the fluctuating friction torque command T Ｂ ＊The approximate maximum value is shown by the dashed line. Figure 4(G) shows the final wheel torque T due to the coordinated action of regenerative braking and friction braking 11. ｗ This graph shows the trend.

[0070] As shown in Figure 4(A), here, time t １ As the accelerator pedal was pressed, the electric vehicle 100 moved at time t ２ The vehicle accelerates at a constant acceleration until a certain point. After that, the electric vehicle 100 decelerates while neither the accelerator pedal nor the brake pedal is operated.

[0071] As shown in Figure 4(C), when the electric vehicle 100 decelerates by regenerative braking, the maximum regenerative torque T is generated due to changes in the state of charge (SOC) of the battery 13, etc. ｒｇ－ｍａｘ It decreases and approaches zero. And here, the maximum regenerative torque T ｒｇ－ｍａｘ is, time t ３ Motor Torque Command T ｍ ＊ (Required torque T) ｒｅｑ It intersects with ) at time t. ３ From now on, the motor torque command T ｍ ＊ Maximum regenerative torque T ｒｇ－ｍａｘ It is restricted.

[0072] On the other hand, time t ３ In addition, the motor torque command T ｍ ＊ (Required torque T) ｒｅｑ ) is the maximum regenerative torque T ｒｇ－ｍａｘ When the value exceeds this, the engine 16 starts running idle, as shown in Figure 4(D). That is, at time t ３ Then, the discharge control of battery 13 is initiated.

[0073] Despite performing discharge control in this manner, the maximum regenerative torque T ｒｇ－ｍａｘ The rate continues to decline, at time t ４ In this case, maximum regenerative torque T ｒｇ－ｍａｘ Motor torque command T limited ｍ ＊ The minimum braking torque T ｍｉｎ When it falls below this value, the friction torque command T is as shown in Figure 4(F). Ｂ ＊This is set. As a result, the electric vehicle 100 uses regenerative cooperative braking, employing both regenerative brakes and friction brakes 11, to achieve a minimum braking torque T ｍｉｎ The system will decelerate with braking torque corresponding to the value.

[0074] Subsequently, as shown in Figure 4(E), time t ５ In this first comparative example, when slippage of the wheel 18 is detected, the motor torque command T is issued as shown in Figure 4(C). ｍ ＊ The value is set to zero, and regenerative braking is turned off. On the other hand, as shown in Figure 4(F), the friction torque command T is activated by the operation of the conventional ABS. Ｂ ＊ It changes in an oscillatory manner.

[0075] Therefore, as shown in Figure 4(G), the wheel torque T ｗ This is the friction torque command T of conventional ABS. Ｂ ＊ This is reflected by significant fluctuations. As a result, vibrations also appear in the vehicle speed V (vehicle speed), as shown in Figure 4(B). In other words, in the first comparative example, even though the vehicle is decelerating with regenerative braking, when slip is detected, the electric vehicle 100 vibrates due to the switch to the conventional ABS.

[0076] Figure 5 shows the motor torque command T for the braking control of this embodiment. ｍ ＊ , friction torque command T Ｂ ＊ , and wheel torque T ｗ This graph schematically shows the changes in the above. The parameters shown in Figure 5 are the same as those in Figure 4. However, in this embodiment, when slip of the wheel 18 is detected, the motor torque command T ｍ ＊ The limited regenerative torque T ｒｇ－ｌｉｍ Since it is limited to this, in Figure 5(C), the limited regenerative torque T ｒｇ－ｌｉｍ The level is indicated by a dotted line.

[0077] As shown in Figure 5(A), here, time t １ As the accelerator pedal was pressed, the electric vehicle 100 moved at time t ２The vehicle accelerates at a constant rate until time t. After that, the electric vehicle 100 decelerates with neither the accelerator pedal nor the brake pedal being operated. In other words, the driving scene described here is the same as in Figure 4. As shown in Figures 5(B) to (G), at time t ４ The changes in each parameter up to that point are the same as in Figure 4.

[0078] On the other hand, as shown in Figure 5(E), time t ５ In this embodiment, when slippage of the wheel 18 is detected, a friction torque command T is issued, as shown in Figure 5(F). Ｂ ＊ The value at the time slip is detected is maintained. Then, as shown in Figure 5(C), the motor torque command T ｍ ＊ This is a limited regenerative torque T corresponding to the slip ratio SR. ｒｇ－ｌｉｍ The motor torque T is set to a value, and the regenerative brake is adjusted to reduce slip. ｍ This is the motor torque command T ｍ ＊ Because it follows changes in the motor torque command T with almost no delay, ｍ ＊ Smooth and rapid limited regenerative torque T ｒｇ－ｌｉｍ It asymptotically approaches.

[0079] Therefore, as shown in Figure 5(G), the wheel torque T ｗ The changes are smooth and rapid. As a result, as shown in Figure 5(B), almost no vibration appears in the vehicle speed V (vehicle speed). In other words, in this embodiment, when slip is detected while decelerating with regenerative cooperative braking, the slip is eliminated by adjusting the regenerative torque, rather than switching to a conventional ABS. This reduces vibration in the electric vehicle 100.

[0080] Figure 6 shows the friction torque T in the second comparative example. Ｂ Motor torque command T when slip is detected before the corresponding braking force is actually generated ｍ ＊ , friction torque command T Ｂ ＊ , and wheel torque T ｗThis graph schematically shows the trends of these factors.

[0081] In the second comparative example, similar to the embodiment, when slippage of the wheel 18 is detected, the friction torque command T Ｂ ＊ The value at the time slip is detected is maintained, and the motor torque command T ｍ ＊ The limited regenerative torque T corresponds to the slip ratio SR. ｒｇ－ｌｉｍ This is an example of setting it to the following. However, in the second comparative example, the friction torque T Ｂ Even if slip is detected before it actually occurs, the friction torque command T Ｂ ＊ Without resetting to zero, the friction torque command T at the time slip is detected Ｂ ＊ Maintain (use) it as is.

[0082] The parameters shown in Figure 6 are the same as those in Figures 4 and 5. However, in Figure 6, the timing at which wheel slip is detected is the same as the timing at which the maximum regenerative torque T is reached. ｒｇ－ｍａｘ Motor torque command T limited ｍ ＊ The minimum braking torque T ｍｉｎ Almost simultaneously with the timing when it falls below (i.e., time t) ４ ) and the actual friction torque T Ｂ This occurs before time t'. In Figure 6(F), the friction torque command T Ｂ ＊ Reflecting the change, the actual friction torque T is generated. Ｂ This is shown by a dashed line. τ shown in Figure 6(F) represents the friction torque command T. Ｂ ＊ After setting, the actual friction torque T Ｂ This is the delay time until the event occurs.

[0083] As shown in Figures 6(E) and 6(F), friction torque command T Ｂ ＊ After setting, the actual friction torque T Ｂ If wheel slip is detected before the slip occurs, in the second comparative example, the friction torque command T at the time the slip is detected is Ｂ ＊The value is maintained. Then, as shown in Figure 6(F), the actual friction torque T is affected by the delay in hydraulic transmission, etc. Ｂ When it occurs with a delay, this delayed friction torque T Ｂ The input is the motor torque command T ｍ ＊ (Regenerative torque limiting T) ｒｇ－ｌｉｍ This becomes a disturbance in the calculation of ). For this reason, as shown in Figure 6(C), the motor torque command T ｍ ＊ The convergence is disrupted, and as shown in Figure 6(G), the friction torque T Ｂ The delayed input is the wheel torque T ｗ This generates vibration. As a result, vibration also appears in the vehicle speed V of the electric vehicle 100, as shown in Figure 6(B). That is, friction torque command T Ｂ ＊ After setting, the actual friction torque T Ｂ When wheel slip is detected before the slip occurs, the initially set friction torque command T Ｂ ＊ If this value is maintained as is, vibrations may occur in the electric vehicle 100.

[0084] Figure 7 shows the friction torque T in the braking control of this embodiment. Ｂ Motor torque command T when slip is detected before the corresponding braking force is actually generated ｍ ＊ , friction torque command T Ｂ ＊ , and wheel torque T ｗ This graph schematically shows the changes in the above. The parameters shown in Figure 7 are the same as in Figure 6. In Figure 7, the timing at which wheel slip is detected corresponds to the maximum regenerative torque T. ｒｇ－ｍａｘ Motor torque command T limited ｍ ＊ The minimum braking torque T ｍｉｎ Almost simultaneously with the timing when it falls below (i.e., time t) ４ ) and the actual friction torque T Ｂ It occurs before the time t'.

[0085] As shown in Figures 7(E) and 7(F), friction torque command T Ｂ ＊After setting, the actual friction torque T Ｂ If slippage of the wheel 18 is detected before the slippage occurs, in this embodiment, the friction torque command T at the time the slippage was detected is immediately applied. Ｂ ＊ The friction torque command T is discarded. Ｂ ＊ It is reset to zero. Therefore, as shown in Figure 7(F), the friction torque T is effectively zero. Ｂ This eliminates the occurrence of friction torque T. Ｂ No disturbance occurs in the form of delayed input.

[0086] Therefore, as shown in Figure 6(C), the motor torque command T ｍ ＊ The convergence is smooth and rapid, as shown in Figure 6(G), and the wheel torque T ｗ Friction torque T Ｂ No vibrations caused by the delayed input appear. As a result, as shown in Figure 6(B), no vibrations appear in the vehicle speed V of the electric vehicle 100. That is, friction torque command T Ｂ ＊ After setting, the actual friction torque T Ｂ Under the special circumstances in which wheel slip of 18 is detected before the friction torque command T occurs, Ｂ ＊ By resetting to zero, the vibration of the electric vehicle 100 is reduced or suppressed.

[0087] Figure 8 shows the limiting regenerative torque T set according to the slip ratio SR in the braking control of this embodiment. ｒｇ－ｌｉｍ Motor torque command T when it becomes a very small value ｍ ＊ , friction torque command T Ｂ ＊ , and wheel torque T ｗ This graph schematically shows the trends of these factors.

[0088] The parameters shown in Figure 8 are the same as those in Figures 4 and 5. However, as shown in Figure 8(E), the slip ratio SR is large here, and as shown in Figure 8(C), the limited regenerative torque T is adjusted according to the slip ratio SR. ｒｇ－ｌｉｍ It is smaller than the reference value ε.

[0089] Thus, the limited regenerative torque T ｒｇ－ｌｉｍ When it becomes a very small value, the friction torque command T Ｂ ＊ Even if this is maintained, it may take a considerable amount of time to resolve the slip, and in some cases, the slip may not be resolved at all. Therefore, in this embodiment, as shown in Figure 8(F), the friction torque command T at the time the slip is detected Ｂ ＊ It is discarded, friction torque command T Ｂ ＊ This is set to zero. Therefore, the braking assistance of the electric vehicle 100 by regenerative cooperative braking is stopped, and the braking of the electric vehicle 100 thereafter is left to the driver's operation of the brake pedal, etc. Note that in Figure 8, time t ５ When a slip occurs, the driver presses the brake pedal to stop the electric vehicle 100.

[0090] As described above, the control method for the electric vehicle according to the above embodiment involves the regenerative torque (T) generated by the electric motor 15. ｍ ) and friction torque T due to friction brake 11 Ｂ This is a control method for electric vehicles that generates braking torque using a friction torque. In this control method, when slip of the wheel 18 is detected in a situation where braking torque is generated using both regenerative torque and friction torque, the friction torque T Ｂ The value is maintained at the point in time when wheel slip of 18 is detected, and the regenerative torque is adjusted.

[0091] Thus, when the electric vehicle 100 is being braked by regenerative cooperative braking and a slip of the wheel 18 is detected, conventionally, the ABS, which uses only the friction brake 11, is activated, causing the electric vehicle 100 to vibrate. In contrast to this, as described above, in regenerative cooperative braking, the friction torque T at the time the slip is detected... Ｂ Maintenance, friction torque T ＢBy adjusting the regenerative torque to a more responsive setting, slippage can be eliminated without causing vibrations in the electric vehicle 100. Furthermore, even when the above-mentioned regenerative cooperative braking is used in combination with conventional ABS, the operation of the conventional ABS is suppressed, making it easier to eliminate slippage without causing vibrations in the electric vehicle 100.

[0092] In the electric vehicle control method according to the above embodiment, the regenerative torque is adjusted by limiting the regenerative torque according to the wheel slip ratio SR.

[0093] In this way, the regenerative torque in regenerative cooperative braking is limited to a regenerative torque T according to the slip ratio SR. ｒｇ－ｌｉｍ Setting it to this value makes it easier to eliminate slippage, especially without causing vibrations in the electric vehicle 100.

[0094] In the electric vehicle control method according to the above embodiment, the friction torque T Ｂ If wheel slip is detected before the corresponding frictional braking force is generated, the value at the time the wheel slip was detected is discarded, and the frictional torque T Ｂ Set it to zero.

[0095] Thus, the actual friction torque T Ｂ If slip is detected before it occurs, the friction torque T at the time of slip detection will be measured. Ｂ (Friction Torque Command T) Ｂ ＊ ) Maintaining this will result in friction torque T Ｂ The delay becomes a disturbance, hindering the convergence of the regenerative torque. As a result, vibration may occur in the electric vehicle 100. In contrast, as described above, the friction torque T Ｂ When slip is detected before it occurs, the friction torque T at the time the slip was detected is... Ｂ Discard the friction torque T Ｂ Setting it to zero results in friction torque T. Ｂ This vibration is virtually eliminated, and the regenerative torque settles smoothly and quickly. As a result, vibrations in the electric vehicle 100 are suppressed.

[0096] In the electric vehicle control method according to the above embodiment, if the regenerative torque after adjustment is less than or equal to a predetermined reference value ε, the value at the time when wheel slip of the 18 is detected is discarded, and the friction torque T Ｂ Set it to zero.

[0097] Thus, when the regenerative torque after adjustment is very small, the regenerative braking system cannot effectively eliminate slip. Therefore, friction torque T Ｂ It is preferable to reset the regenerative braking system to zero, stop the braking assistance provided by the regenerative braking system, and leave the braking of the electric vehicle 100 to the driver's operation of the brake pedal, etc. This allows the electric vehicle 100 to slip without interfering with the braking operation using the brake pedal, etc.

[0098] In the electric vehicle control method according to the above embodiment, the braking torque is set to a minimum value (minimum braking torque T). ｍｉｎ The maximum regenerative torque T is set in advance and is the maximum regenerative torque that the electric motor 15 can generate. ｒｇ－ｍａｘ The minimum value is (T ｍｉｎ If the value is greater than or equal to the maximum regenerative torque T, the regenerative torque will generate braking torque, and the maximum regenerative torque T will be generated. ｒｇ－ｍａｘ The minimum value is (T ｍｉｎ If it is smaller than ), the maximum regenerative torque T ｒｇ－ｍａｘ While generating the minimum value (T ｍｉｎ Maximum regenerative torque T ｒｇ－ｍａｘ To compensate for the deficiency, friction torque T Ｂ By setting this, the regenerative torque and friction torque T Ｂ Braking torque is generated using both of these methods.

[0099] Thus, in regenerative braking, the minimum braking torque T ｍｉｎ When setting this, the braking control of the above embodiment is particularly effective in eliminating slippage without causing vibration in the electric vehicle 100.

[0100] In the electric vehicle control method according to the above embodiment, the maximum regenerative torque T ｒｇ－ｍａｘ The minimum value is (T ｍｉｎ If it is smaller than ), the battery 13 that supplies power to the electric motor 15 is discharged, thereby achieving the maximum regenerative torque T ｒｇ－ｍａｘThis increases the maximum regenerative torque T due to the discharge of battery 13. ｒｇ－ｍａｘ Even if increased, the maximum regenerative torque T ｒｇ－ｍａｘ The minimum value is (T ｍｉｎ When it is smaller than ), the friction torque T Ｂ Set it.

[0101] Thus, in principle, the maximum regenerative torque T is achieved by discharging the battery 13. ｒｇ－ｍａｘ It increases the maximum regenerative torque T ｒｇ－ｍａｘ The minimum braking torque T ｍｉｎ When it is smaller than, friction torque T Ｂ It is preferable to set the friction torque T as much as possible. Ｂ By adjusting the regenerative torque to be more responsive, vibrations in the electric vehicle 100 can be suppressed more easily.

[0102] The control device for the electric vehicle according to the above embodiment is a control device (controller 12) for the electric vehicle 100 that generates braking torque using regenerative torque from the electric motor 15 and friction torque from the friction brake. When the control device (controller 12) detects slip of the wheel 18 in a situation where braking torque is generated using both regenerative torque and friction torque, it generates friction torque T Ｂ The system includes a friction brake control unit 30 that maintains the value at the time of detecting wheel slip 18, and an electric motor control unit 28 that adjusts the regenerative torque when wheel slip is detected in a situation where braking torque is generated using both regenerative torque and friction torque.

[0103] Thus, when the electric vehicle 100 is being braked by regenerative cooperative braking and a slip of the wheel 18 is detected, conventionally, the ABS, which uses only the friction brake 11, is activated, causing the electric vehicle 100 to vibrate. In contrast to this, as described above, in regenerative cooperative braking, the friction torque T at the time the slip is detected... Ｂ Maintenance, friction torque T ＢBy adjusting the regenerative torque to a more responsive setting, slippage can be eliminated without causing vibrations in the electric vehicle 100. Furthermore, even when the above-mentioned regenerative cooperative braking is used in combination with conventional ABS, the operation of the conventional ABS is suppressed, making it easier to eliminate slippage without causing vibrations in the electric vehicle 100.

[0104] Although embodiments and modifications of the present invention have been described above, the configurations described in the above embodiments and modifications represent only a part of the application examples of the present invention and are not intended to limit the technical scope of the present invention.

Claims

1. A control method for an electric vehicle that generates braking torque using regenerative torque from an electric motor and friction torque from a friction brake, wherein when wheel slip is detected in a situation where the braking torque is generated using both the regenerative torque and the friction torque, the control method for an electric vehicle maintains the friction torque at the value at the time the wheel slip was detected and adjusts the regenerative torque.

2. A method for controlling an electric vehicle according to claim 1, wherein the adjustment of the regenerative torque is performed by limiting the regenerative torque according to the slip ratio of the wheels.

3. A control method for an electric vehicle according to claim 1, wherein if a slip of the wheel is detected before a frictional braking force corresponding to the friction torque is generated, the value at the time the slip of the wheel is detected is discarded and the friction torque is set to zero.

4. A control method for an electric vehicle according to claim 1, wherein, if the regenerative torque after adjustment is less than or equal to a predetermined reference value, the value at the time when wheel slip is detected is discarded and the friction torque is set to zero.

5. A control method for an electric vehicle according to claim 1, comprising: setting a minimum value for the braking torque in advance; generating the braking torque using the regenerative torque when the maximum regenerative torque, which is the maximum regenerative torque that the electric motor can generate, is equal to or greater than the minimum value; and generating the braking torque using both the regenerative torque and the friction torque when the maximum regenerative torque is less than the minimum value, while generating the maximum regenerative torque, by setting the friction torque to compensate for the deficiency of the maximum regenerative torque relative to the minimum value.

6. A method for controlling an electric vehicle according to claim 5, wherein, when the maximum regenerative torque is less than the minimum value, the maximum regenerative torque is increased by discharging the battery that supplies power to the electric motor, and when the maximum regenerative torque is still less than the minimum value even after increasing the maximum regenerative torque by discharging the battery, the friction torque is set.

7. A control device for an electric vehicle that generates braking torque using regenerative torque from an electric motor and friction torque from a friction brake, comprising: a friction brake control unit that maintains the friction torque at the value at the time the wheel slip was detected when the wheel slip is detected in a situation in which the braking torque is generated using both the regenerative torque and the friction torque; and an electric motor control unit that adjusts the regenerative torque when the wheel slip is detected in a situation in which the braking torque is generated using both the regenerative torque and the friction torque.

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