Electric vehicle control device

Abstract

To achieve both vibration damping control and slippage suppression control in an electric vehicle.SOLUTION: A control device of an electric vehicle using a motor as a drive force source includes a slip suppression part for suppressing slippage of driving wheels when a slippage ratio of the driving wheels of the electric vehicle becomes equal to or higher than a prescribed threshold, a vibration damping control part for executing vibration damping control of suppressing the vibration of the electric vehicle, and a grip determination part for determining whether or not the driving wheels grip a road surface, wherein the vibration damping control part stops the vibration damping control when it is determined by the grip determination part that the driving wheels do not grip the road surface, and executes the vibration damping control when it is determined by the grip determination part that the driving wheels grips the road surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a control device for an electric vehicle. [Background technology]

[0002] Conventionally, there is known a technique for performing vibration damping control and slip suppression control while an electric vehicle, such as an electric vehicle or a hybrid vehicle, is driven by an electric motor (Patent Document 1). The control device described in Patent Document 1 prevents the behavior of the vehicle from becoming unstable by not performing vibration damping control while vehicle slip suppression control is being executed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-081853 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even while slip suppression control is being executed, it is believed that the wheels will be gripping the road surface immediately before the slip suppression control ends. In the control device described in Patent Document 1, vibration suppression control is not executed while vehicle slip suppression control is being executed, which causes a problem that vibration suppression control is excessively suppressed even when the wheels are gripping the road surface and the vehicle behavior is stable. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms. According to one aspect of the present disclosure, there is provided a control device for an electric vehicle, the control device including: a slip suppression unit that performs slip suppression control to suppress slip of a drive wheel of the electric vehicle when a slip ratio of the drive wheel is equal to or less than a predetermined threshold; a vibration suppression control unit that performs vibration suppression control to suppress vibration of the electric vehicle; and a grip determination unit that determines whether the drive wheel is gripping a road surface, wherein the vibration suppression control unit stops the vibration suppression control when the grip determination unit determines that the drive wheel is not gripping the road surface, and performs the vibration suppression control even during execution of the slip suppression control when the grip determination unit determines that the drive wheel is gripping the road surface.

[0006] (1) According to one aspect of the present disclosure, there is provided a control device for an electric vehicle that uses a motor as a driving force source, the control device including: a slip suppression unit that suppresses slip of a drive wheel of the electric vehicle when a slip ratio of the drive wheel is equal to or greater than a preset threshold; a vibration suppression control unit that executes vibration suppression control that suppresses vibration of the electric vehicle; and a grip determination unit that determines whether the drive wheel is gripping a road surface, wherein the vibration suppression unit stops the vibration suppression control when the grip determination unit determines that the drive wheel is not gripping the road surface, and executes the vibration suppression control when the grip determination unit determines that the drive wheel is gripping the road surface. According to this type of control device, even if slip suppression control is being performed by the slip suppression unit, vibration control is performed if the grip determination unit determines that the drive wheels are gripping the road surface, thereby preventing the vibration suppression control from being excessively suppressed. (2) In the above embodiment, the slip suppression unit may instantaneously increase the output torque of the motor when the grip determination unit determines that the drive wheels are not gripping the road surface. According to this type of control device, when the grip determination unit determines that the drive wheels are not gripping the road surface, the output torque of the motor is instantaneously increased, thereby promoting the drive wheels to grip the road surface and shortening the time required to recover from a slip state. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is an explanatory diagram showing the configuration of a vehicle equipped with a control device of the present embodiment; [Figure 2] 4 is a flowchart showing a procedure of a vehicle control process according to the present embodiment. [Figure 3] 4 is a flowchart showing a procedure of a vehicle control process according to the present embodiment. [Figure 4] 4 is a timing chart showing an example of a vehicle control process according to the present embodiment. [Figure 5]4 is a flowchart showing the procedure of a first slip process according to the present embodiment. [Figure 6] 4 is a flowchart showing a procedure for a re-slip process according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. Implementation: A-1.Device configuration: 1 is an explanatory diagram showing the configuration of a vehicle 100 equipped with a control device 50 of this embodiment. In this embodiment, the vehicle 100 is an electric vehicle equipped with a motor as a driving power source, or an electric vehicle configured as a hybrid vehicle equipped with a motor and an engine. The vehicle 100 includes front wheels 10, rear wheels 20, a motor 30, a power transmission mechanism 40, and the control device 50.

[0009] The motor 30 generates torque by receiving power from a battery system (not shown). The motor 30 also generates regenerative power when the vehicle 100 decelerates and supplies the power to the battery system.

[0010] In this embodiment, the vehicle 100 is configured as a front-wheel drive vehicle, and the front wheels 10 are driven by torque received from a motor 30 via a power transmission mechanism 40. The power transmission mechanism 40 includes a transmission and a shaft. The front wheels 10 correspond to the "drive wheels" in this disclosure. The rear wheels 20 are driven in accordance with the movement of the vehicle 100 driven by the front wheels 10.

[0011] The control device 50 acquires information from various devices and sensors mounted on the vehicle 100. In this embodiment, the control device 50 acquires the accelerator opening from an accelerator pedal 61, the brake pedal force from a brake pedal 62, the vehicle speed from a vehicle speed sensor 63, the rotation speed of the front wheels 10 from a front wheel speed sensor 64, the rotation speed of the rear wheels 20 from a rear wheel speed sensor 65, the shift position from a shift lever 66, and a signal corresponding to the motor rotation speed from a resolver 67 installed in the motor 30.

[0012] The control device 50 is configured as an ECU having a CPU 51 and a memory 52. ​​The CPU 51 executes programs stored in advance in the memory 52, thereby functioning as a slip suppression unit 511, a vibration damping control unit 512, and a grip determination unit 513.

[0013] The slip suppression unit 511 executes slip suppression control to suppress slip of the drive wheels. More specifically, in order to suppress slip of the drive wheels, the slip suppression unit 511 sets a limit torque that is greater than the torque required by the driver (hereinafter also referred to as "required torque"), and controls the output torque of the motor 30 in accordance with the limit torque. The slip suppression unit 511 calculates the required torque using the accelerator opening degree obtained from the accelerator pedal 61 and the brake pedal force obtained from the brake pedal 62.

[0014] The vibration suppression control unit 512 executes vibration suppression control to suppress vibrations of the vehicle 100. More specifically, the vibration suppression control unit 512 uses the required torque and a preset vibration model to estimate vibrations of the vehicle 100 that occur due to changes in the required torque, and controls the output torque of the motor 30 so as to suppress such vibrations.

[0015] The grip determination unit 513 determines whether the front wheels 10 are gripping the road surface. In this embodiment, the grip determination unit 513 calculates a slip ratio to determine whether the drive wheels are gripping the road surface. The "slip ratio" refers to an index that indicates the slip state of the front wheels 10 relative to the road surface. In this embodiment, the slip ratio is calculated by taking the difference in rotation speed between the front wheels 10, which are drive wheels, and the rear wheels 20, which are driven wheels. In this embodiment, the slip ratio decreases as the difference in rotation speed between the front wheels 10 and the rear wheels 20 increases, in other words, as the degree of slippage worsens.

[0016] A-2. Vehicle control processing: 2 and 3 are flowcharts showing the procedure of the vehicle control process of this embodiment. Also, Fig. 4 is a timing chart showing an example of the vehicle control process of this embodiment. The vehicle control process is repeatedly executed while the control device 50 is running.

[0017] 2, the vibration suppression control unit 512 starts vibration suppression control. Thereafter, the control device 50 executes the processes from step S4 to step S10 and the processes from step S12 to step S32 in parallel.

[0018] In step S4, the grip determination unit 513 determines whether the slip ratio is less than a preset threshold value THs. While it is determined that the slip ratio is equal to or greater than the set threshold value THs (step S4: No), the grip determination unit 513 repeatedly executes this determination.

[0019] If it is determined that the slip ratio is less than the set threshold value THs (step S4: Yes), grip determination unit 513 switches slip determination to "ON," and vibration damping control unit 512 stops vibration damping control (step S6). If the slip ratio is less than the set threshold value THs, the drive wheels may slip, and vibration damping control unit 512 may not be able to estimate vibrations in accordance with the required torque. In such a situation, vibration damping control may be performed based on erroneously estimated vibrations, which may increase vibrations and make the running state of vehicle 100 more unstable, so vibration damping control unit 512 stops vibration damping control. In FIG. 4, at time T1 and time T5, slip determination is switched from "OFF" to "ON," and vibration damping control is stopped.

[0020] In step S8 shown in Fig. 2, the grip determination unit 513 determines whether the slip ratio is greater than the reset threshold value THr. The reset threshold value THr is set as a slip ratio greater than the set threshold value THs described above, in other words, as a slip ratio in a driving state in which the degree of slippage is alleviated. While it is determined that the slip ratio is less than the reset threshold value THr (step S8: No), the grip determination unit 513 repeatedly executes this determination.

[0021] If it is determined that the slip ratio is greater than reset threshold value THr (step S8: Yes), grip determination unit 513 switches slip determination to "OFF," and vibration damping control unit 512 resumes vibration damping control (step S10). In FIG. 4, at times T3 and T7, slip determination is switched from "ON" to "OFF," and vibration damping control is resumed. After step S10 is completed, grip determination unit 513 executes step S4 again.

[0022] In step S12 shown in FIG. 2, the slip suppression unit 511 determines whether the running state of the vehicle 100 satisfies the slip suppression control start condition. In this embodiment, the slip suppression unit 511 determines whether all of the following conditions (a1) to (a5) are satisfied. By using (a1) to (a5) as the slip suppression control start conditions, slip suppression control can be started when there is a high possibility that slip has actually occurred. While it is determined that the slip suppression control start condition is not satisfied (step S12: No), the slip suppression unit 511 repeatedly executes this determination. (a1) Slip detection is "ON." (a2) The shift position is in the forward range. (a3) The strong regeneration mode is selected as the driving mode. (a4) There is no torque restriction due to a vehicle abnormality. (a5) The required torque is equal to or less than a threshold value that is preset for each vehicle speed.

[0023] 2, if it is determined that the slip prevention control start condition is satisfied (step S12: Yes), the slip prevention unit 511 starts slip prevention control (step S14) and executes the initial slip process (step S16). The initial slip process is executed not only when the slip prevention control start condition is satisfied for the first time since the control device 50 is started, but also when the slip prevention control start condition is satisfied again after the slip prevention control termination condition, which will be described later, is satisfied. FIG. 4 shows a timing chart for the case where the slip determination is switched to "ON" at time T1, thereby satisfying (a1), and all of the conditions (a1) to (a5) are satisfied.

[0024] FIG. 5 is a flowchart showing the procedure for the initial slip process of this embodiment. In step S1610, the slip suppression unit 511 instantaneously increases the torque to a preset magnitude. Increasing the torque promotes the drive wheels' grip on the road surface and allows the drive wheels to quickly recover from a slipping state. Here, "instantaneously increasing" means increasing the torque to a preset magnitude within a time shorter than the time required for torque increase due to accelerator operation during normal driving, for example, within one second. The torque increase amount in this step is determined in advance by simulation or the like as a magnitude that does not cause the driving situation of the vehicle 100 to become unstable.

[0025] In step S1620, slip suppression unit 511 determines whether or not the slip determination is “OFF.” If the slip determination is “OFF” (step S1620: Yes), slip suppression unit 511 ends the first slip process.

[0026] If the slip determination is "ON" (step S1620: No), slip suppression unit 511 repeatedly executes step S1620 until a preset waiting time Δt1 has elapsed (step S1630: No).

[0027] After the waiting time Δt1 has elapsed (step S1630: Yes), in other words, after the waiting time Δt1 has elapsed after step S1610 without the slip determination being switched to "OFF," the slip suppression unit 511 switches the low μ road determination to "ON" and starts gradually increasing the torque (step S1640). Since the slip state is not alleviated even after the waiting time Δt1 has elapsed after the torque increase in step S1610, the slip state is alleviated by further increasing the torque. In FIG. 4, the waiting time Δt1 has elapsed at time T2, the low μ road determination is switched to "ON," and the gradual increase in torque starts. The torque increase rate is determined in advance through experiments or the like to be large enough to prevent the driver from feeling uncomfortable due to acceleration fluctuations when the slip state is resolved and the drive wheels grip the road surface.

[0028] 5, in step S1650, slip suppression unit 511 determines whether or not the slip determination is “OFF.” While it is determined that the slip determination is “ON” (step S1650: No), slip suppression unit 511 repeatedly executes this determination and continues to gradually increase the torque.

[0029] If it is determined that the slip determination is "OFF" (step S1650: Yes), slip suppression unit 511 stops the gradual increase of torque and acquires the torque when the gradual increase is stopped (hereinafter also referred to as "torque when the gradual increase is stopped") (step S1660). This ends the first slip processing. In FIG. 4, the gradual increase of torque is stopped at time T3.

[0030] In step S18 of FIG. 2, the slip suppression unit 511 waits until a preset waiting time Δt2 has elapsed (step S18: No). After the waiting time Δt2 has elapsed (step S18: Yes), the slip suppression unit 511 starts gradually reducing the torque (step S20). If the gradual reduction of the torque starts immediately after the slip determination is switched to "OFF," the slip state may worsen again and the running state may become unstable. Therefore, the slip suppression unit 511 waits until the waiting time Δt2 has elapsed and the running state has stabilized before starting the gradual reduction of the torque. In FIG. 4, the waiting time Δt2 has elapsed at time T4, and the gradual reduction of the torque starts.

[0031] 3, the slip suppression unit 511 determines whether the slip determination is "ON." If it is determined that the slip determination is "ON" (step S22: Yes), the slip suppression unit 511 executes re-slip processing (step S24). The slip suppression unit 511 executes re-slip processing when the slip determination is switched from "ON" to "OFF" once and then switched from "OFF" to "ON" again during execution of slip suppression control.

[0032] FIG. 6 is a flowchart showing the procedure for the re-slip process of this embodiment. In step S2410, the slip suppression unit 511 stops the gradual decrease in torque and starts a gradual increase. Note that in the first-slip process described above, the slip suppression unit 511 instantaneously increases the torque, but in the re-slip process of this embodiment, such torque control is not performed. This is because, in the case of a re-slip, the running state of the vehicle 100 is considered to be more stable than in the case of the first slip due to the first-slip process being performed, and therefore, the urgency of recovering from the slip state is not as high as in the case of the first slip. In FIG. 4, the gradual decrease in torque is stopped and the gradual increase in torque is started at time T5.

[0033] 6, slip suppression unit 511 determines whether the slip determination is “OFF.” If it is determined that the slip determination is “OFF” (step S2420: Yes), slip suppression unit 511 stops the gradual increase in torque (step S2430) and ends the re-slip process.

[0034] If it is determined that the slip determination is "ON" (step S2420: No), slip suppression unit 511 determines whether the torque has reached the upper limit torque (step S2422). The upper limit torque is a value obtained by adding a preset additional value to the gradually increasing stop torque acquired in the above-mentioned step S1660. If it is determined that the upper limit torque has not been reached (step S2422: No), slip suppression unit 511 executes step S2420 again.

[0035] If it is determined that the upper limit torque has been reached (step S2422: Yes), slip suppression unit 511 stops the gradual increase of the torque (step S2432). Fig. 4 shows a timing chart in which the upper limit torque is reached at time T6.

[0036] In step S2442 shown in FIG. 6, slip suppression unit 511 determines whether or not the slip determination is "OFF." While it is determined that the slip determination is "ON" (step S2442: No), slip suppression unit 511 holds the torque at the upper limit torque and waits. If it is determined that the slip determination is "OFF" (step S2442: Yes), slip suppression unit 511 ends the re-slip process. In FIG. 4, the slip determination is switched to "OFF" at time T7.

[0037] After the re-slip process is completed, the slip suppression unit 511 again executes step S18 shown in Fig. 2. In Fig. 4, the waiting time Δt2 elapses at time T8, and the gradual decrease in torque starts.

[0038] If the slip determination is "OFF" in step S22 shown in Fig. 3 (step S22: No), the slip suppression unit 511 determines whether the limit torque is less than the required torque. If the limit torque is equal to or greater than the required torque (step S26: No), the slip suppression unit 511 executes step S22 again. If it is determined that the limit torque is less than the required torque (step S26: Yes), the slip suppression unit 511 controls the braking / driving of the vehicle 100 in accordance with the required torque (step S28). In Fig. 4, at time T9, the torque that has been gradually decreasing in accordance with the limit torque becomes less than the required torque.

[0039] In step S30, the slip suppression unit 511 determines whether or not the running state of the vehicle 100 satisfies a slip suppression control termination condition. In this embodiment, the slip suppression unit 511 determines whether or not at least one of the following conditions (b1) to (b4) is satisfied. (b1) The shift position is other than the forward range. (b2) The slip determination is "OFF" and the required torque is greater than a threshold value that is preset for each vehicle speed. (b3) The requested torque is greater than the torque obtained by adding a hysteresis of a preset magnitude to the limit torque. (b4) The required torque becomes greater than the limit torque, and the state in which the required torque is greater than the limit torque continues for a preset time.

[0040] If it is determined that the slip suppression control termination condition is met (step S30: Yes), the slip suppression unit 511 switches the low μ road determination to "OFF" and terminates the slip suppression control (step S32). FIG. 4 shows a timing chart for when the slip suppression control termination condition is met by satisfying (b3) at time T10. Thereafter, the vibration suppression control unit 512 executes step S2 again. As described above, the control device 50 repeatedly executes vehicle control.

[0041] According to the control device 50 of the embodiment described above, even if the slip suppression unit 511 is executing slip suppression control, if the grip determination unit 513 determines that the drive wheels are gripping the road surface, vibration suppression control is executed, thereby preventing the vibration suppression control from being excessively suppressed.

[0042] In addition, when the grip determination unit 513 determines that the drive wheels are not gripping the road surface, the slip suppression unit 511 instantaneously increases the output torque of the motor 30, thereby promoting the drive wheels to grip the road surface and shortening the time required to recover from a slip state.

[0043] B. Other Embodiments: (B1) In the above embodiment, the vehicle 100 is configured as a front-wheel drive vehicle, but the present disclosure is not limited to this. The vehicle 100 may be configured as a rear-wheel drive vehicle or a four-wheel drive vehicle. The control device 50 mounted on such a vehicle 100 also achieves the same effects as the above embodiment.

[0044] (B2) In the above embodiment, the grip determination unit 513 calculates the slip ratio by taking the difference between the rotation speeds of the front wheels 10 and the rear wheels 20, but the present disclosure is not limited to this. The grip determination unit 513 may calculate the slip ratio by taking the difference between the motor rotation speed and the rotation speed of the rear wheels 20.

[0045] (B3) In the above embodiment, slip suppression unit 511 executes step S1610 in the first slip processing, but the present disclosure is not limited to this. Slip suppression unit 511 may execute step S1620 in the first slip processing without executing step S1610. Even with control device 50 of this configuration, excessive suppression of vibration damping control can be suppressed.

[0046] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0047] 10...front wheels, 20...rear wheels, 30...motor, 40...power transmission mechanism, 50...control device, 51...CPU, 52...memory, 61...accelerator pedal, 62...brake pedal, 63...vehicle speed sensor, 64...front wheel speed sensor, 65...rear wheel speed sensor, 66...shift lever, 67...resolver, 100...vehicle, 511...slip suppression unit, 512...vibration damping control unit, 513...grip determination unit

Claims

1. A control device for an electric vehicle that uses a motor as a driving force source, a slip suppression unit that performs slip suppression control to suppress slip of the drive wheels when a slip ratio of the drive wheels of the electric vehicle becomes equal to or less than a preset threshold value; a vibration damping control unit that performs vibration damping control to suppress vibrations of the electric vehicle; a grip determination unit that determines whether the drive wheels are gripping a road surface; Equipped with The vibration damping control unit is When the grip determination unit determines that the drive wheels are not gripping the road surface, the vibration damping control is stopped; When the grip determination unit determines that the drive wheels are gripping the road surface, the vibration damping control is executed even during execution of the slip suppression control. Control device.

2. The control device according to claim 1, the slip suppression unit momentarily increases the output torque of the motor when the grip determination unit determines that the drive wheels are not gripping the road surface. Control device.

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