Control device for electric vehicle

Abstract

To smoothly travel over a step even by one pedal-operation.SOLUTION: A control device for an electric vehicle includes: a motor that drives a driving wheel of a vehicle; an acceleration sensor that measures an acceleration of the vehicle; a vehicle speed sensor that measures a speed of the vehicle; and a control unit that controls the motor according to an amount of operation of an accelerator pedal. When detecting or estimating a rebound of the vehicle from a step of a road surface, based on the acceleration measured by the acceleration sensor and the speed measured by the vehicle speed sensor, the control unit controls the motor to increase a driving force of the vehicle.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device for an electric vehicle.

Background Art

[0002] As an invention related to a vehicle capable of performing a one-pedal operation in which a motor is used as a power source, the vehicle is accelerated by depressing a pedal, and the vehicle is decelerated by releasing the pedal, for example, there is a vehicle control device disclosed in Patent Document 1. This control device increases the driving force corresponding to the operation amount of the depression operation from a predetermined reference point on the accelerator pedal to accelerate the vehicle, decreases the driving force corresponding to the operation amount of the release operation from the predetermined reference point, and generates a braking force to decelerate the vehicle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the vehicle travels off-road, on a rocky road, it may travel over steps such as rocks. In this case, for example, in an automatic vehicle with an engine as a drive source, while traveling with the driving force of the creep phenomenon without depressing the accelerator, the brake pedal is further operated to suppress the speed and move forward. When the tire collides with a step during the vehicle's travel, since the driving force of the creep phenomenon and the braking force by the brake are greater than the reaction force from the step, it is possible to suppress the tire from bouncing back against the step and cross the step. On the other hand, when traveling off-road with a one-pedal operation, the pedal is depressed to suppress the speed and the vehicle travels without operating the brake pedal. However, when the tire contacts a step, the driving force by the one-pedal operation is small, and there is no braking force by the brake against the reaction force from the step. Therefore, there is a problem that the tire bounces back against the step and cannot cross the step smoothly.

[0005] The present invention has been made in view of the above, and an object thereof is to smoothly overcome a step even with one-pedal operation and travel.

Means for Solving the Problems

[0006] The control device for an electric vehicle according to the present invention includes a motor that drives drive wheels of the vehicle, an acceleration sensor that measures an acceleration of the vehicle, a vehicle speed sensor that measures a speed of the vehicle, and a control unit that controls the motor according to an operation amount of an accelerator pedal. The control unit increases a driving force of the vehicle by controlling the motor when detecting a bounce of the vehicle against a step on the road surface or estimating that the vehicle bounces against a step on the road surface based on the acceleration measured by the acceleration sensor and the speed measured by the vehicle speed sensor.

[0007] Thereby, even when the wheels collide with a step on the road surface and receive a reaction force from the step, the driving force can be increased so that the vehicle can overcome the step.

[0008] Further, in the above, when the speed measured by the vehicle speed sensor is equal to or lower than a predetermined threshold value and a bounce of the vehicle against a step on the road surface is detected, the control unit may control the motor to increase the driving force of the vehicle.

[0009] Thereby, at a speed exceeding a predetermined speed, even if the wheels collide with a step on the road surface, the driving force is not increased, and it is possible to prevent the speed from becoming excessive.

[0010] Further, in the above, when braking by the brake of the vehicle is not being performed and a bounce of the vehicle against a step on the road surface is detected, the control unit may control the motor to increase the driving force of the vehicle.

[0011] Thereby, when being braked by the driver using the brake, it is possible to prevent accelerating against the driver's intention.

[0012] Further, in the above, when the driving mode of the vehicle is the off-road mode and the vehicle's bounce against the road surface step is detected, the control unit may control the motor to increase the driving force of the vehicle.

[0013] Thereby, when the wheel collides with the road surface step, the driving force can be increased only during off-road driving, and the vehicle can overcome the step.

Effect of the Invention

[0014] The control device for an electric vehicle according to the present invention has an effect that it can smoothly overcome steps and travel even with one-pedal operation.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described in detail based on the drawings. Note that the present invention is not limited by the embodiments described below.

[0017] [Embodiment] FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle 1 according to an embodiment of the present invention. The vehicle 1 is, for example, a battery electric vehicle (BEV), and includes a pair of drive wheels 2a, a pair of driven wheels 2b, a differential gear 4, a drive shaft 5, and an MG (motor generator) 6. The MG 6 is a three-phase AC motor generator that serves as a power source for driving the drive wheels 2a of the vehicle 1, and an output shaft 6a is connected to the differential gear 4. The pair of driven wheels 2b are front wheels located at the front of the vehicle 1, and the pair of drive wheels 2a are rear wheels located at the rear of the vehicle 1. The pair of drive wheels 2a are respectively connected to both ends of the drive shaft 5. The drive shaft 5 is connected to the differential gear 4. The drive wheels 2a generate a driving force when the torque output by the MG 6 described later is transmitted through the output shaft 6a, the differential gear 4, and the drive shaft 5. Note that the vehicle 1 may be a front-wheel drive vehicle that transmits the torque output by the MG 6 to the front wheels to generate a driving force. Further, the vehicle 1 may be a four-wheel drive vehicle that transmits the torque output by the MG 6 to both the front wheels and the rear wheels to generate a driving force.

[0018] In addition, the vehicle 1 includes a battery 7, an ECU (electronic control unit) 10, and a PCU (power control unit) 11. The battery 7 is a secondary battery capable of repeated charging and discharging, and is electrically connected to the PCU 11. The PCU 11 is a device that controls the power supplied between the battery 7 and the MG 6, and is electrically connected to the MG 6. Further, the PCU 11 is communicably connected to the ECU 10 and is controlled by the ECU 10. The PCU 11 includes a DC-DC converter (not shown) and an inverter (not shown). The DC-DC converter steps up and steps down DC power, and the inverter converts between DC power and AC power. The battery 7 is connected to the MG 6 via the DC-DC converter and the inverter.

[0019] The vehicle 1 is a vehicle capable of one-pedal operation that accelerates by depressing the accelerator pedal 22 and decelerates by releasing it. When the vehicle 1 accelerates or travels at a constant speed by depressing the accelerator pedal 22, power is supplied from the battery 7 to the MG6 via the PCU11. In this case, the DC power from the battery 7 is stepped up in the DC-DC converter and further converted into AC power by the inverter and supplied to the MG6. When power is supplied to the MG6, the torque output by the MG6 is transmitted via the output shaft 6a, the differential gear 4, and the drive shaft 5, causing the drive wheels 2a to rotate and the vehicle 1 to travel. Also, when the vehicle 1 decelerates by releasing the accelerator pedal 22 (not shown), the MG6 functions as a generator and power is supplied from the MG6 to the battery 7 via the PCU11 to charge the battery 7. In this case, the AC power from the MG6 is converted into DC power by the inverter and further stepped down in the DC-DC converter and supplied to the battery 7.

[0020] An example of the control unit, the ECU 10, includes a processor, a RAM (Random Access Memory), a ROM (Read Only Memory), and an input / output interface. The input / output interface has the torque sensor 12, the vehicle speed sensor 13, the acceleration sensor 14, the brake sensor 15, and the accelerator position sensor 16 electrically connected thereto. The input / output interface is an interface that acquires the measurement results of the torque sensor 12, the vehicle speed sensor 13, the acceleration sensor 14, the brake sensor 15, and the accelerator position sensor 16, and performs communication with the PCU 11 and the like. The input / output interface acquires the measurement results of various sensors and outputs a signal for controlling the PCU 11. The RAM is composed of a volatile memory. The RAM serves as a work space when the processor performs arithmetic processing, and stores the results of the processor's arithmetic processing and the like. The ROM is composed of a non-volatile memory. The ROM stores a program used by the processor to perform arithmetic processing. The processor reads the program from the ROM and executes it using the RAM as a work space. When the processor of the ECU 10 executes the program, a function of controlling the torque output by the MG 6 by communicating with the PCU 11 is realized. That is, the driving force of the vehicle 1 is controlled by the ECU 10. Also, when the processor executes the program, a function of enabling the vehicle 1 to smoothly cross a step in off-road is realized.

[0021] The torque sensor 12 is a sensor that measures the torque of the output shaft 6a, and outputs a signal indicating the measurement result to the ECU 10. The vehicle speed sensor 13 is a sensor that measures the speed of the vehicle 1, and outputs a signal indicating the measurement result to the ECU 10. The acceleration sensor 14 is a sensor that measures the acceleration of the vehicle 1, and outputs a signal indicating the measurement result to the ECU 10. The brake sensor 15 is a sensor that measures the amount of depression of the brake pedal 21 by the user, and outputs a signal indicating the measurement result to the ECU 10. The accelerator position sensor 16 is a sensor that measures the operation amount of the accelerator pedal 22, and outputs a signal indicating the measurement result to the ECU 10.

[0022] Next, an operation example of the ECU 10 will be described. FIG. 2 is a flowchart showing the flow of the step-over process executed by the ECU 10. When the power switch of the vehicle 1 is on, the ECU 10 acquires the measurement results of the torque sensor 12, the vehicle speed sensor 13, the acceleration sensor 14, and the brake sensor 15 at a predetermined cycle, and repeatedly executes the process of FIG. 2.

[0023] First, the ECU 10 determines whether the driving mode of the vehicle 1 is the off-road mode (step S1). The vehicle 1 is provided with a driving mode corresponding to the road surface condition, and the ECU 10 optimizes the driving force, the brake, the suspension, etc. according to the mode set by the driver using a switch (not shown). The off-road mode is a mode in which control suitable for driving on a rocky road is performed.

[0024] If the driving mode set by the driver is not the off-road mode (No in step S1), the ECU 10 ends the step-over process. If the driving mode set by the driver is the off-road mode (Yes in step S1), in order to limit the execution of the control to cross the step to a situation of driving at a low speed like on a rocky road, the ECU 10 determines whether the vehicle 1 is driving at a low speed (step S2). Here, if the speed measured by the vehicle speed sensor 13 exceeds a predetermined threshold (No in step S2), the ECU 10 ends the step-over process. This threshold is, for example, the speed at which the vehicle travels in a creep phenomenon.

[0025] If the speed measured by the vehicle speed sensor 13 is equal to or lower than a predetermined threshold (Yes in step S2), the ECU 10 determines whether the vehicle 1 contacts the step and bounces back (step S3). Here, the ECU 10 determines whether the vehicle 1 contacts the step and bounces back based on, for example, the measurement results of the acceleration sensor 14 and the vehicle speed sensor 13 acquired at a predetermined cycle.

[0026] FIG. 3 is a diagram showing an example of changes in the acceleration, vehicle speed, and driving force of the vehicle 1 during low-speed driving. For example, when the front wheels of the vehicle 1 collide with a step such as a rock at time t1, a force in the direction opposite to the traveling direction of the vehicle 1 acts on the vehicle 1, so that the acceleration measured by the acceleration sensor 14 becomes a negative value as shown in FIG. 3. The ECU 10 estimates whether the vehicle 1 contacts the step and bounces back from the acceleration measured by the acceleration sensor 14 and the vehicle speed measured by the vehicle speed sensor 13. When the acceleration measured by the acceleration sensor 14 is equal to or less than a predetermined threshold value (a1) and the vehicle speed measured by the vehicle speed sensor 13 is equal to or less than a predetermined threshold value (v1), the ECU 10 determines that the vehicle 1 contacts the step and bounces back (Yes in step S3). Further, when the acceleration measured by the acceleration sensor 14 exceeds a predetermined threshold value (a1) or the vehicle speed measured by the vehicle speed sensor 13 exceeds a predetermined threshold value (v1), the ECU 10 determines that the vehicle 1 does not bounce back from the step (No in step S3). Note that the ECU 10 estimates whether the vehicle speed becomes negative based on the change rate per unit time of the acceleration measured by the acceleration sensor 14 and the vehicle speed measured by the vehicle speed sensor 13. When it is estimated that the vehicle speed becomes negative, the ECU 10 may determine Yes in step S3, and when it is estimated that the vehicle speed does not become negative, the ECU 10 may determine No in step S3.

[0027] When the ECU 10 determines No in step S3, the ECU 10 ends the step-over process. On the other hand, when the ECU 10 determines Yes in step S3, the ECU 10 determines whether the brake pedal 21 of the vehicle 1 is depressed (step S4). When the depression amount of the brake pedal 21 measured by the brake sensor 15 is equal to or more than a predetermined threshold value and braking is performed by the brake, the ECU 10 determines that the brake pedal 21 is depressed (No in step S4) and ends the step-over process.

[0028] On the one hand, when the depression amount of the brake pedal 21 measured by the brake sensor 15 is less than a predetermined threshold value, the ECU 10 determines that the brake pedal 21 is not depressed (Yes in step S4), and corrects the driving force (step S5). Here, the ECU 10 calculates the driving force of the drive wheel 2a from the measurement result of the torque sensor 12, and calculates the driving force required for the driven wheel 2b to overcome the step as shown by the broken line in FIG. 3 based on the vehicle speed measured by the vehicle speed sensor 13, the acceleration measured by the acceleration sensor 14, and the calculated driving force.

[0029] The ECU 10 calculates the torque that can obtain the calculated driving force, and instructs the PCU 11 to output the calculated torque. The PCU 11 controls the MG6 to output the torque instructed by the ECU 10. By controlling the driving force of the drive wheel 2a in this way, the vehicle speed and the driving force change as shown by the broken line in FIG. 3. After executing the process of step S5, the ECU 10 returns the process flow to step S3. If it is determined No in step S3 or step S4, the step-over process ends.

[0030] As described above, according to the present embodiment, even in the one-pedal operation without operating the brake pedal 21, the vehicle 1 can smoothly overcome the step and travel. Further, in the present embodiment, even when the wheel collides with the step on the road surface and receives the reaction force from the step, the driving force can be increased so that the vehicle 1 can overcome the step. Further, in the present embodiment, at a speed exceeding a predetermined speed, even if the wheel collides with the step on the road surface, the driving force is not increased, and the speed can be prevented from becoming excessive. Further, in the present embodiment, when the vehicle is being braked by the operation of the driver's brake pedal 21, it is possible to prevent acceleration against the driver's intention. Further, in the present embodiment, when the wheel collides with the step on the road surface, the driving force can be increased only when off-road, and the vehicle can overcome the step.

[0031] [Modification Example] As described above, the embodiments of the present invention have been explained. However, the present invention is not limited to the above-described embodiments and can be implemented in various other forms. For example, the present invention may be implemented by modifying the above-described embodiments as follows. Note that the above-described embodiments and the following modification examples may be combined with each other. The present invention also includes those configured by appropriately combining the constituent elements of the above-described embodiments and each modification example. Further, additional effects and modification examples can be easily derived by those skilled in the art. Therefore, a broader aspect of the present invention is not limited to the above-described embodiments and modification examples, and various changes are possible.

[0032] The vehicle 1 is not limited to an electric vehicle, and may be a vehicle that runs on electric power such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a fuel cell electric vehicle (FCEV).

[0033] In the above-described embodiment, the driving force of the vehicle 1 is calculated using the measurement result of the torque sensor 12. However, the driving force of the vehicle 1 may be calculated by measuring the current flowing through the MG6 with a current sensor or calculating the torque output by the MG6 based on the voltage applied to the MG6, and using this calculation result.

[0034] In the present invention, when the vehicle 1 is a vehicle equipped with a transmission, in the above-described step S1, if it is a low gear, step S2 may be executed, and if it is not a low gear, the step-over process may be terminated.

[0035] In the present invention, when the vehicle speed becomes negative after the acceleration becomes negative during low-speed driving, the ECU 10 may determine that the vehicle 1 has contacted a step and bounced back, and further execute the process of step S5 when the brake pedal 21 is not depressed.

Explanation of Reference Numerals

[0036] 1 Vehicle 2a Driving wheel 2b Driven wheel 6 MG 7 Battery 10 ECU 11 PCU 12 Torque sensor 13 Vehicle speed sensor 14 Acceleration sensor 15 Brake sensor 16 Accelerator position sensor 21 Brake pedal 22 Accelerator pedal

Claims

1. A motor that drives the drive wheels of a vehicle; an acceleration sensor for measuring the acceleration of the vehicle; A vehicle speed sensor for measuring the speed of the vehicle; A control unit that controls the motor in response to an amount of depression of an accelerator pedal; having When the control unit detects the vehicle bouncing off a step on a road surface based on the acceleration measured by the acceleration sensor and the speed measured by the vehicle speed sensor, or when the control unit estimates that the vehicle will bounce off a step on a road surface, the control unit controls the motor to increase the driving force of the vehicle. A control device for an electric vehicle.

2. The control unit controls the motor to increase the driving force of the vehicle when the speed measured by the vehicle speed sensor is equal to or lower than a predetermined threshold and a bounce of the vehicle against a step on a road surface is detected. The control device for an electric vehicle according to claim 1.

3. The control unit controls the motor to increase the driving force of the vehicle when braking of the vehicle is not being performed and a bounce of the vehicle against a step on a road surface is detected. The control device for an electric vehicle according to claim 1.

4. The control unit controls the motor to increase a driving force of the vehicle when the driving mode of the vehicle is an off-road mode and the control unit detects the vehicle bouncing off a step on a road surface. The control device for an electric vehicle according to claim 1.

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