KR-102962187-B1 - REGENERATIVE BRAKING CONTROL METHOD FOR MOTOR DRIVING VEHICLE

KR102962187B1KR 102962187 B1KR102962187 B1KR 102962187B1KR-102962187-B1

Abstract

The present invention aims to provide a regenerative braking control method for an eco-friendly vehicle that enables the simultaneous improvement of fuel efficiency and vehicle driving stability by implementing regenerative braking control subdivided according to road surface conditions and driving conditions, maximizing regenerative braking intervention when driving stability is secured, and performing cooperative control with ABS and ESC in addition to regenerative braking when driving stability is additionally secured under various driving conditions.

Inventors

정종규

Assignees

현대자동차주식회사
기아 주식회사

Dates

Publication Date: 20260508
Application Date: 20200514

Claims (14)

A step of determining whether the vehicle is in a high-speed driving state to determine the high-speed driving state if the current vehicle speed exceeds a reference vehicle speed, after confirming that the accelerator pedal and brake pedal are in a released state where regenerative braking is possible; A step of determining whether to turn by comparing the steering angle with a reference steering angle while the vehicle is driving at high speed; A step of determining whether the vehicle is in an emergency evasive steering state in which the steering angular velocity exceeds a reference steering angular velocity during high-speed cornering; A control step for reducing regenerative braking torque based on the average of the inner and outer wheel speeds in the turning direction when the vehicle is in a high-speed driving state and the steering angle is confirmed to be less than the reference steering angle; A control step for reducing regenerative braking torque based on the outer wheel speed in the turning direction when the vehicle is in a high-speed driving state and in a turning state where the steering angle exceeds a reference steering angle, and it is confirmed that the steering angular velocity is less than the reference steering angular velocity; A control step for reducing regenerative braking torque based on the inner wheel speed in the turning direction when it is confirmed that the vehicle is in a high-speed driving state, in a turning state exceeding a reference steering angle, and in an emergency evasive steering state where the steering angular velocity exceeds the reference steering angular velocity; A regenerative braking cooperative control method for an eco-friendly vehicle characterized by including
In claim 1, In a control step for reducing regenerative braking torque based on the average of the inner and outer wheel speeds in the aforementioned turning direction, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized by reducing the regenerative braking torque by a predetermined reduction rate in proportion to the increased vehicle speed relative to the set vehicle speed, based on the average of the inner and outer wheel speeds in the turning direction, since the steering angle is less than the reference steering angle even though the vehicle is in a high-speed driving state.
In claim 2, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized in that when control to reduce regenerative braking torque based on the average of inner and outer wheel speeds in the aforementioned turning direction is performed, if the entry condition for ABS control is satisfied, regenerative braking control and ABS control are performed together.
In claim 3, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized in that when the entry condition for the above ABS control is not met, the control for reducing the above regenerative braking torque is maintained as long as the release of the accelerator pedal and the brake pedal is maintained.
In claim 1, In a control step for reducing regenerative braking torque based on the outer wheel speed in the aforementioned turning direction, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized by determining a general steering condition in which the steering angular velocity is less than the reference steering angular velocity, and reducing the regenerative braking torque by a predetermined reduction rate in proportion to the magnitude of the increased vehicle speed relative to the set vehicle speed, based on the outer wheel speed in the turning direction.
In claim 5, When a control step for reducing regenerative braking torque based on the outer wheel speed in the aforementioned turning direction is performed, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized by further performing an Ackermann yaw rate correction step that estimates the yaw rate (Δr) changing due to the above regenerative braking torque and reflects it in the Ackermann yaw rate (r).
In claim 6, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized in that, after the Ackermann yaw rate correction step, if it is confirmed that the yaw rate error, which is the difference between the Ackermann yaw rate and the actual yaw rate, exceeds a reference value and the tire pressure of the outer wheel exceeds a reference value, control to reduce the regenerative braking torque and ESC control to stabilize the vehicle's behavior are performed together.
In claim 7, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized in that if it is confirmed that the yaw rate error, which is the difference between the Ackermann yaw rate and the actual yaw rate, does not exceed a reference value, or that the tire pressure of the outer wheel does not exceed a reference value, the control for reducing the regenerative braking torque is maintained as long as the release of the accelerator pedal and the brake pedal is maintained.
In claim 1, In a control step for reducing regenerative braking torque based on the inner wheel speed in the aforementioned turning direction, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized by determining an emergency evasive steering state in which tire side slip at the outer wheel in the turning direction is instantaneously increased while the outer wheel speed is instantaneously significantly lower than the inner wheel speed, and reducing the regenerative braking torque by a predetermined reduction rate in proportion to the increased vehicle speed relative to the set vehicle speed, based on the inner wheel speed which is higher than the outer wheel speed in the turning direction.
In claim 9, When a control step for reducing regenerative braking torque based on the inner wheel speed in the aforementioned turning direction is performed, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized by further performing an Ackermann yaw rate correction step that estimates the yaw rate (Δr) changing due to the above regenerative braking torque and reflects it in the Ackermann yaw rate (r).
In claim 10, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized in that, after the Ackermann yaw rate correction step, if it is confirmed that the yaw rate error, which is the difference between the Ackermann yaw rate and the actual yaw rate, exceeds a reference value and the tire pressure of the outer wheel exceeds a reference value, the control for reducing the regenerative braking torque is terminated and ESC control is performed.
In claim 11, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized in that if it is confirmed that the yaw rate error, which is the difference between the Ackermann yaw rate and the actual yaw rate, does not exceed a reference value, or that the tire pressure of the outer wheel does not exceed a reference value, control to reduce the regenerative braking torque is maintained as long as the release of the accelerator pedal and the brake pedal is maintained.
In claim 1, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized by further proceeding with a step of determining whether the road surface condition causes unstable driving stability before confirming that the accelerator pedal and brake pedal are in a released state capable of regenerative braking, and confirming that the accelerator pedal and brake pedal are in a released state when it is confirmed that the road surface condition causes unstable driving stability.
In claim 13, In the step of determining whether the above road surface condition causes unstable driving stability, A regenerative braking cooperative control method for an eco-friendly vehicle, characterized by determining that unstable road surface conditions cause driving stability when a rain sensor is activated or when the color of the road surface in front captured by a front vision sensor is determined to be white and TCS intervention occurs.

Description

Regenerative Braking Cooperative Control Method for Eco-friendly Vehicles The present invention relates to a regenerative braking cooperative control method for an eco-friendly vehicle, and more specifically, to a regenerative braking cooperative control method for an eco-friendly vehicle that enables simultaneous improvement in fuel efficiency and driving stability by implementing regenerative braking control subdivided according to driving conditions. As is well known, hybrid vehicles, electric vehicles, hydrogen fuel cell vehicles, etc., are equipped with motors as a driving force, and such vehicles are referred to as eco-friendly vehicles or electrified vehicles. In addition to driving for driving, the motor is controlled to perform regenerative braking that converts the vehicle's kinetic energy into electrical energy under driving conditions such as constant speed and deceleration or coasting on a downhill slope, as shown in FIG. 1. The above-mentioned regenerative braking refers to a method in which, when driving a vehicle, the motor generates back electromotive force and operates as a generator to produce electrical energy under the OFF condition when the foot is taken off the accelerator pedal or the ON condition when the brake pedal is pressed, and the produced electrical energy is charged into the battery, thereby enabling an improvement in fuel efficiency. For example, under the above accelerator pedal off condition, regenerative braking force (e.g., at the level of 0.1 to 0.3g) can be generated to minimize driver discomfort while simultaneously charging electric energy into the battery, and under the above brake pedal on condition, the brake fluid pressure (= hydraulic braking force) can be raised to a predetermined level and held, while simultaneously generating auxiliary braking force according to the above regenerative braking to obtain a deceleration corresponding to the braking force required by the driver (e.g., brake fluid pressure 0.5g + regenerative braking 0.2g = braking deceleration equivalent to 0.7g). However, since regenerative braking is mostly engaged under accelerator pedal off conditions solely to maximize fuel efficiency improvement without road surface condition judgment or feedback control regarding driving conditions, a method to change the regenerative braking deceleration conditions according to road surface and driving conditions is required. Meanwhile, conventionally, in addition to the regenerative braking control mentioned above, ABS (Anti-lock Brake System) control, which includes braking control to prevent wheel lock-up during sudden braking, and ESC (Electronic Stability Control) control, which includes braking control to prevent vehicle slippage and stabilize the vehicle body posture, are performed independently. An example thereof can be seen by referring to the flowchart of the attached FIG. 2. First, check whether the driver has taken their foot off the accelerator pedal while driving, i.e., whether the accelerator pedal is released (S201), and if the accelerator pedal is released, determine the driver's intention to brake by checking whether the brake pedal is on (S202). The driver's intention to brake can be determined by whether the brake pedal is in the ON state, as the brake switch turns ON when the brake pedal is pressed. If the brake pedal is in the ON state as a result of the judgment in step S202 above, hydraulic braking and regenerative braking by the hydraulic braking device are performed together (S203), and accordingly, a deceleration (e.g., 0.3 ~ 0.5g) can be obtained to satisfy the braking force required by the driver. At this time, the condition for intervention of the ABS or ESC control is determined (S204), and if the condition for separate braking control by the ABS or ESC is satisfied, the regenerative braking is immediately terminated and the ABS or ESC control is performed first (S205). Meanwhile, if the result of the judgment in step S202 is that the brake pedal is off, regenerative braking control is performed such that deceleration is achieved by a step-by-step coast regenerative torque that can be determined by the driver, i.e., the regenerative braking torque of the motor due to the vehicle's inertia driving or coasting driving (S206). By the above regenerative braking control, a deceleration (e.g., 0.05 to 0.3g) can be obtained to satisfy the driver's required braking force. More specifically, the regenerative braking deceleration (e.g., 0.05 ~ 0.3g) is determined by the negative torque generated by the back EMF of the motor due to the vehicle's inertial driving or coasting, that is, the drive motor or the hybrid starter generator (HSG) for starting the engine and generating power of the hybrid vehicle, and the battery is also charged by the power generation operation of the drive motor (S207). At this time, if it is determined whether the ABS control intervention condition is satisfied and it is confirmed that ABS control is not pos