Regenerative braking system using reference deceleration speed during vehicle coasting drive and its method

Abstract

The present invention relates to a regenerative braking system, and more specifically, to a regenerative braking system characterized by comprising: a front vehicle recognition module installed in a vehicle to determine the presence or absence of a vehicle ahead and to measure information regarding the relative distance and relative speed to the vehicle ahead; a vehicle sensor installed in the vehicle; and a control unit that, when the vehicle coasts while a vehicle ahead is detected by the front vehicle recognition module, receives information generated from the front vehicle recognition module and a sensor signal generated from the vehicle sensor, generates a reference deceleration rate to maintain the distance to the vehicle ahead within a safe distance, generates a driving torque command to output a regenerative braking torque that follows the generated reference deceleration rate, and transmits the command to the vehicle's drivetrain.

Description

Technology Field

[0001] The present invention relates to a regenerative braking system, and more specifically, to a regenerative braking system characterized by comprising: a front vehicle recognition module installed in a vehicle to determine the presence or absence of a vehicle ahead and to measure information regarding the relative distance and relative speed to the vehicle ahead; a vehicle sensor installed in the vehicle; and a control unit that, when the vehicle coasts while a vehicle ahead is detected by the front vehicle recognition module, receives information generated from the front vehicle recognition module and a sensor signal generated from the vehicle sensor, generates a reference deceleration rate to maintain the distance to the vehicle ahead within a safe distance, generates a driving torque command to output a regenerative braking torque that follows the generated reference deceleration rate, and transmits the command to the vehicle's drivetrain. Background Technology

[0002] Generally, a hybrid electric vehicle (abbreviated as 'HEV') refers to a vehicle that runs using driving force provided by an engine and a motor, while an electronic vehicle (abbreviated as 'EV') refers to a vehicle that runs using driving force provided by a motor.

[0003] In such hybrid electric vehicles or electric vehicles, driving force is provided by a motor when starting or at a speed below a certain level, and when driving at a constant speed with high fuel efficiency, driving force is provided by an engine while simultaneously operating a generator to charge a battery that supplies power to the motor.

[0004] At this time, if the driver does not press either the accelerator or the brake while the vehicle is in motion, coasting is performed, in which the vehicle moves by inertia, and the regenerative braking function is activated during this coasting.

[0005] Generally, the above regenerative braking function refers to a situation where, when a vehicle coasts or the brake pedal is pressed, the power supplied to the motor is cut off, but a back EMF is generated from the motor by the wheels rotating due to the vehicle's forward inertia, and when this back EMF is applied to the motor again, a regenerative braking torque is generated to cause a reverse torque to be generated in the motor, thereby generating a braking force of the vehicle.

[0006] Since such regenerative braking can achieve additional fuel efficiency improvements through energy recovery, there is a continuous demand for methods to implement it more efficiently. The problem to be solved

[0007] The present invention is proposed to resolve the various problems of the prior art as described above, and provides a regenerative braking system and method capable of preventing unnecessary energy consumption and obtaining additional fuel efficiency improvement by automatically generating a regenerative braking amount based on the distance or relative speed with respect to a vehicle ahead during coasting, and thereby performing optimized regenerative braking in situations requiring deceleration. means of solving the problem

[0008] The configuration of the regenerative braking system and method using a reference deceleration rate during coasting of a vehicle according to the present invention for achieving the above technical objectives is characterized by comprising: a front vehicle recognition module installed in a vehicle to determine the presence or absence of a vehicle ahead and to measure information regarding the relative distance and relative speed to the vehicle ahead; a vehicle sensor installed in the vehicle; and a control unit that, when the vehicle coasts while a vehicle ahead is detected by the front vehicle recognition module, receives information generated from the front vehicle recognition module and a sensor signal generated from the vehicle sensor, generates a reference deceleration rate capable of maintaining the distance to the vehicle ahead within a safe distance, generates a driving torque command to output a regenerative braking torque that follows the generated reference deceleration rate, and transmits the command to the vehicle's drivetrain. Effects of the invention

[0009] The regenerative braking system and method using the reference deceleration of the present invention, having the above-described configuration, has the effect of improving driving convenience by maximizing the reduction effect of APS and BPS inputs in the vehicle following situation according to the relative distance and relative speed with respect to the vehicle ahead during coasting of the vehicle.

[0010] In addition, since it performs deceleration based on information about the vehicle ahead regardless of driver intervention, it has the effect of enhancing the driving stability of the vehicle.

[0011] In addition, the amount of regenerative braking corresponding to various driving situations on the road is automatically generated, and by performing optimized regenerative braking in situations requiring deceleration, the effect of improved fuel efficiency is achieved. Brief explanation of the drawing

[0012] FIG. 1 is a block diagram of the regenerative braking system of the present invention, FIG. 2 is a conceptual diagram of a CA model used in the regenerative braking system of the present invention. FIG. 3 is a conceptual diagram of a CTG policy model used in the regenerative braking system of the present invention. FIG. 4 is a graph showing the acceleration of the CA model and the acceleration of the CTG policy model used in the regenerative braking system of the present invention, the usage ratio of the CA model, and the sum of the acceleration of the CA model and the acceleration of the CTG policy model. FIG. 5 is a flowchart of the regenerative braking method of the present invention. Specific details for implementing the invention

[0013] Hereinafter, the configuration and operation of the regenerative braking system and method using a reference deceleration rate during coasting of an automobile according to the present invention will be described in detail with reference to the drawings.

[0014] However, the disclosed drawings are provided as examples to ensure that the concept of the present invention is sufficiently conveyed to those skilled in the art. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other aspects.

[0015] Furthermore, unless otherwise defined, terms used in this specification have the meaning commonly understood by those skilled in the art to which this invention pertains, and detailed descriptions of known functions and configurations that could unnecessarily obscure the essence of the invention are omitted in the following description and accompanying drawings.

[0016] Figure 1 is a block diagram of the regenerative braking system of the present invention.

[0017] The regenerative braking system of the present invention utilizes a calculation model for the safe distance between a user's own vehicle (hereinafter referred to as the "user vehicle" for convenience of explanation) and another person's vehicle (hereinafter referred to as the "front vehicle" for convenience of explanation) driving in front of the user vehicle. When the vehicle coasts while the front vehicle is detected by the front vehicle recognition module, the system calculates a reference deceleration rate and determines the amount of regenerative braking according to the calculated reference deceleration rate. This enables the user vehicle to continuously maintain driving stability even in the event of a sudden acceleration of the front vehicle or an unexpected situation where another vehicle suddenly cuts in front of the user vehicle. Through this, the operating range of the regenerative system can be expanded from the conventionally limited vehicle speed range to the entire vehicle speed range.

[0018] Referring to FIG. 1, the regenerative braking system of the present invention comprises a front vehicle recognition module (10) mounted on a vehicle, such as a radar or camera, which determines the presence or absence of a vehicle ahead and measures information on the relative distance and relative speed to the vehicle ahead; vehicle sensors (20), such as a vehicle speed sensor, an accelerator pedal recognition sensor (APS), a brake pedal recognition sensor (BPS), and a longitudinal acceleration sensor, which are mounted on the vehicle; and a control unit (100) which, when the vehicle coasts while a vehicle ahead is detected by the front vehicle recognition module (10), receives information generated from the front vehicle recognition module (10) and sensor signals generated from the vehicle sensors (20), generates a reference deceleration rate that can maintain the distance to the vehicle ahead within a safe distance, generates a driving torque command to output a regenerative braking torque that follows the generated reference deceleration rate, and transmits it to the vehicle's drive system (200).

[0019] And, the drive system (200) of the vehicle that receives the above drive torque command applies regenerative braking torque to the motor of the vehicle according to the drive torque command, thereby enabling regenerative braking of the vehicle while it is in motion.

[0020] At this time, the control unit (100) may operate according to the control of the electronic control unit (ECU) of the vehicle or may operate independently of the control of the electronic control unit (ECU).

[0021] The drive system (200) of the above vehicle is a part that receives a drive torque command generated by the control unit (100) and drives the motor of a hybrid electric vehicle or an electric vehicle.

[0023] The regenerative braking system of the present invention as described above will be explained in more detail.

[0024] The control unit (100) comprises: a deceleration necessity determination unit (110) that determines whether regenerative braking operation is required based on a sensor signal input from the vehicle sensor (20), and if it is determined that regenerative braking operation is required, determines whether deceleration of the vehicle is required based on information of the vehicle ahead input from the vehicle ahead recognition module (10); a reference deceleration generation unit (120) that generates a reference deceleration rate according to the driving conditions of the vehicle using information of the vehicle ahead input from the vehicle ahead recognition module (10) and a sensor signal input from the vehicle sensor (20) if it is determined that deceleration of the vehicle is required by the deceleration necessity determination unit (110); and a driving torque amount generation unit (130) that generates a driving torque command to output a regenerative braking torque that follows the generated reference deceleration rate and transmits it to the vehicle drive system (200).

[0025] Preferably, the deceleration necessity determination unit (110) determines whether regenerative braking operation is necessary based on the input value of the accelerator pedal recognition sensor (ASP) among the vehicle sensors (20), and receives information on the relative distance and relative speed between the user vehicle and the vehicle ahead from the front vehicle recognition module (10) to determine whether deceleration of the vehicle is necessary.

[0026] Additionally, preferably, the reference deceleration generation unit (120) generates a reference deceleration according to the current driving condition of the user vehicle based on the information on the relative distance and relative speed between the user vehicle and the vehicle ahead input from the vehicle recognition module (10) and the speed and acceleration sensor signals of the user vehicle and the vehicle ahead input from the vehicle sensor (20).

[0027] More preferably, the reference deceleration generation calculates the reference deceleration (a_ref) by using together the constant acceleration model acceleration value (a_ca) calculated using a constant acceleration (CA) model based on the information on the relative distance and relative speed and the sensor signals of speed and acceleration, and the CTG policy model acceleration value (a_ctg) calculated using a CTG policy (CTG policy) model based on the information on the relative distance and relative speed and the sensor signals of speed and acceleration.

[0029] Hereinafter, the equivalent acceleration model and the CTG policy model according to the present invention will be described in more detail.

[0030] FIG. 2 is a conceptual diagram of a CA model used in the regenerative braking system of the present invention, and FIG. 3 is a conceptual diagram of a CTG policy model used in the regenerative braking system of the present invention.

[0031] First, with reference to FIG. 2, a configuration for calculating an equivalent acceleration model acceleration value (a_ca) using a CA model according to an embodiment of the present invention will be explained.

[0032] The CA model according to the embodiment of the present invention calculates an equal acceleration model acceleration value (a_ca) using the following mathematical formula 1 based on information regarding the speed of the user vehicle (v_ego), the speed of the vehicle ahead (v_pre), and the distance (d) between the user vehicle and the vehicle ahead.

[0034] (Mathematical Formula 1)

[0035]

[0036] *(1) represents mathematical formula 1

[0038] In addition, the constant acceleration model acceleration value (a_ca) can be calculated using the following mathematical formula 2, and mathematical formula 2 takes into account the different tendencies of the driver and the driver of the user's vehicle at the speed of the vehicle ahead.

[0040] (Mathematical Formula 2)

[0041]

[0042] * v_res: Represents the margin of speed. A positive value means decelerating faster than the vehicle ahead, while a negative value means decelerating slower than the vehicle ahead.

[0044] Next, with reference to FIG. 3, a configuration for calculating the CTG policy model acceleration value (a_ctg) calculated using the CTG policy (Constant Time Gap policy, abbreviated as 'CTG policy') model according to an embodiment of the present invention will be described.

[0045] The CTG policy model according to the embodiment of the present invention is a model that calculates the safety distance from the vehicle ahead differently depending on the speed of the user vehicle. First, based on the information of the speed of the user vehicle (v_ego), the speed of the vehicle ahead (v_pre), the distance between the user vehicle and the vehicle ahead (d_rei), and the minimum distance between the user vehicle and the vehicle ahead (d_min), the safety distance (L_des) is set in proportion to the speed of the user vehicle using the following mathematical formula 3.

[0047] (Mathematical Formula 3)

[0048]

[0049] * h: Time Headway

[0050] *(3) represents mathematical formula 3

[0052] h in the above Equation 3 is the value of the time head-to-head interval, which refers to the time from when the head of the vehicle ahead passes a certain point until the head of the vehicle following passes a point for vehicles traveling continuously in the same lane, and the larger the value of h, the greater the safety distance calculated at the same vehicle speed.

[0053] Next, when the safety distance (L_des) is set in proportion to the speed of the user vehicle according to the above mathematical formula 3, each of the following mathematical formulas 4 to 8 is calculated sequentially to calculate the CTG policy model acceleration value (a_ctg) that can maintain the safety distance between the user vehicle and the vehicle ahead.

[0055] (Mathematical Formula 4)

[0056]

[0057] * δ: spacing error value

[0058] *(4) represents mathematical formula 4

[0060] (Mathematical Formula 5)

[0061]

[0062] *(5) represents mathematical formula 5

[0064] (Mathematical Formula 6)

[0065]

[0066] * ε: d_min (-) d_rei

[0067] *(6) represents mathematical formula 6

[0069] (Mathematical Formula 7)

[0070]

[0071] * a_ctg: CTG policy model acceleration value

[0072] *λ: tuning parameter (The larger the value of λ, the faster the relative distance converges to the safe distance)

[0073] *(7) represents mathematical formula 7

[0075] (Mathematical Formula 8)

[0076]

[0077] * a_ctg: CTG policy model acceleration value

[0078] * v_rei: Relative speed between the user's vehicle and the vehicle ahead

[0079] *(8) represents mathematical formula 8

[0081] Next, the reference deceleration (a_ref) is calculated using the following Equations 9 and 10 by combining the constant acceleration model acceleration value (a_ca) calculated by Equation 1 or Equation 2 above and the CTG policy model acceleration value (a_ctg) calculated by Equation 7 or Equation 8 above.

[0083] (Mathematical Formula 9)

[0084]

[0085] * w_ca: Weight of the constant acceleration model acceleration value (a_ca)

[0086] * w_ctg: Weight of CTG policy model acceleration value (a_ctg)

[0087] The weights (w_ca) of the above constant acceleration model acceleration value (a_ca) and the weights (w_ctg) of the CTG policy model acceleration value (a_ctg) can be adjusted according to various variables that can represent the vehicle following situation (e.g., speed of the vehicle, relative distance, time headway with the preceding vehicle, etc.).

[0088] *(9) represents mathematical formula 9

[0090] (Mathematical Formula 10)

[0091]

[0092] *(10) represents mathematical formula 10

[0094] For reference, we will examine various application examples of the weight (w_ca) of the constant acceleration model acceleration value (a_ca) and the weight (w_ctg) of the CTG policy model acceleration value (a_ctg) by referring to the following Examples 1 to 4.

[0096] (Example 1)

[0097] Case where only the constant acceleration model is used when the relative distance between the user vehicle and the vehicle ahead is 30m or more, a combination of the constant acceleration model and CTG policy is used in the range between 30m and 10m, and only the CTG model is used for distances of 10m or less:

[0098]

[0100] (Example 2)

[0101] When using only the constant acceleration model if the time remaining until collision between the user vehicle and the vehicle ahead is 1.6s or more, using a combination of the constant acceleration model and CTG policy in the interval between 1.6s and 1.2s, and using only the CTG model if it is 1.2s or less:

[0102]

[0104] (Example 3)

[0105] Case where only the constant acceleration model is used when the user vehicle speed is 20 m / s or higher, a combination of the constant acceleration model and CTG policy is used in the range between 20 m / s and 10 m / s, and only the CTG model is used at 10 m / s or lower:

[0106]

[0108] (Example 4)

[0109] Case where only the constant acceleration model is used when the speed of the vehicle ahead is 20 m / s or higher, a combination of the constant acceleration model and the CTG policy is used in the range between 20 m / s and 10 m / s, and only the CTG model is used at 10 m / s or lower:

[0110]

[0112] Figure 4 is a graph showing the acceleration of the CA model and the acceleration of the CTG policy model used in the regenerative braking system of the present invention, the usage ratio of the CA model, and the sum of the acceleration of the CA model and the acceleration of the CTG policy model.

[0113] Referring to the drawing, in the graph of an example of CA and CTG acceleration at the top of the drawing, according to an example of the usage ratio of the CA model according to an embodiment of the present invention in the middle of the drawing, when the reference deceleration (a_ref) is calculated by using the constant acceleration model acceleration value (a_ca) and the CTG policy model acceleration value (a_ctg) together according to Equations 9 and 10, the graph of the calculated reference deceleration (a_ref) appears as shown at the bottom of the drawing.

[0115] Next, a regenerative braking method according to an embodiment of the present invention will be described in detail with reference to FIG. 5.

[0116] Referring to the drawings, the regenerative braking method of the embodiment of the present invention is a regenerative braking method performed by the forward recognition module (10), vehicle sensor (20), and control unit (100) as described above, and each step is specifically explained as follows.

[0117] First, the control unit (100) monitors the signal input from the accelerator pedal sensor (APS) of the vehicle sensor (20) (S1).

[0118] Next, during the monitoring process, the control unit (100) determines whether the value of the sensor signal of the accelerator pedal recognition sensor is less than a preset first reference value, and determines whether the user vehicle is accelerating with the accelerator pedal pressed (S2).

[0119] The above first threshold value may be changed according to the sensor characteristics of the accelerator pedal recognition sensor (APS sensor), and if the APS sensor value is less than the first threshold value, it is determined that the user vehicle is in a state of coasting because the accelerator pedal is not pressed, and if it exceeds the first threshold value, it is determined that the user vehicle is in a state of accelerating because the accelerator pedal is pressed.

[0120] Next, if the result of the judgment in step S2 is below the first threshold and the user vehicle is coasting, the control unit (100) monitors the information of the vehicle ahead input from the vehicle ahead recognition module (10) (S3).

[0121] On the other hand, if the result of the judgment in step S2 above is greater than or equal to the first threshold value, the monitoring in step S1 above is continued.

[0122] And, the control unit (100) determines (S4) whether the relative speed between the user vehicle and the vehicle ahead is less than 0 during the monitoring process of step S3, and determines whether the user vehicle in motion needs to decelerate.

[0123] Here, if the value of the relative speed between the user vehicle and the vehicle ahead is less than 0, it indicates a case where the current speed of the user vehicle is faster than the speed of the vehicle ahead, and a state requiring deceleration by regenerative braking to maintain the distance from the vehicle ahead within a safe distance.

[0124] However, if the value of the relative speed is 0 or greater, it indicates a case where the current user vehicle's speed is slower than the speed of the vehicle ahead, and deceleration by regenerative braking is not required.

[0125] If, as a result of the judgment in step S4 above, the user vehicle in motion requires deceleration, the control unit (100) generates a reference deceleration rate that allows the distance to the vehicle in motion to be maintained within a safe distance using information of the vehicle in motion input from the vehicle recognition module (10) and sensor signals input from the vehicle sensor (20) (S5). The control unit (100) generates a driving torque command to output a regenerative braking torque that follows the generated reference deceleration rate and transmits it to the vehicle's drive system (200) so that the regenerative braking torque is applied to the vehicle's motor (S6), thereby decelerating the user vehicle in motion and enabling regenerative braking operation according to the deceleration.

[0126] Accordingly, by automatically performing regenerative braking while coasting a vehicle by means of the regenerative braking method of the present invention as described above, considering the distance and speed to the vehicle ahead, not only can the safety of the vehicle in motion be improved, but fuel efficiency can also be enhanced through the operation of regenerative braking, and the driver can drive more comfortably by minimizing the input of the accelerator pedal and brake pedal during the situation of following the vehicle ahead. Explanation of the symbols

[0127] * Explanation of symbols for major parts of the drawing * 10; Front vehicle recognition module 20; vehicle sensor 100; control unit 110; Deceleration necessity determination unit 120; Reference deceleration generation unit 130; Driving torque amount generating unit

Claims

Claim 1 A regenerative braking system for a vehicle comprises: a front vehicle recognition module (10) installed in the vehicle to determine the presence or absence of a vehicle ahead and to measure information regarding the relative distance and relative speed to the vehicle ahead; a vehicle sensor (20) installed in the vehicle; and a control unit (100) that, when the vehicle coasts while the vehicle ahead is detected by the front vehicle recognition module (10), receives information generated from the front vehicle recognition module (10) and sensor signals generated from the vehicle sensor (20), generates a reference deceleration rate that can maintain the distance to the vehicle ahead within a safe distance, generates a driving torque command to output a regenerative braking torque that follows the generated reference deceleration rate, and transmits the driving torque command to the vehicle's drive system. The vehicle's drive system (200), having received the driving torque command, applies regenerative braking torque to the vehicle's motor according to the driving torque command, and the control unit (100) determines whether regenerative braking operation is required according to the sensor signal input from the vehicle sensor (20). The system includes a deceleration necessity determination unit (110) that determines whether deceleration of the vehicle is necessary based on information of the vehicle ahead input from the vehicle ahead recognition module (10) when it is determined that regenerative braking operation is necessary, and a reference deceleration generation unit (120) that generates a reference deceleration according to the driving condition of the vehicle using information of the vehicle ahead input from the vehicle ahead recognition module (10) and a sensor signal input from the vehicle sensor (20) when it is determined that deceleration of the vehicle is necessary by the deceleration necessity determination unit (110), and a driving torque amount generation unit (130) that generates a driving torque command to enable the vehicle in motion to follow the reference deceleration generated by the reference deceleration generation unit (120) and transmits it to the vehicle drive system (200), wherein the reference deceleration generation unit (120) includes information on the relative distance and relative speed between the user vehicle and the vehicle ahead input from the vehicle ahead recognition module (10) and the A reference deceleration rate is generated according to the current driving condition of the user vehicle based on the speed and acceleration sensor signals of the user vehicle and the vehicle ahead input from the vehicle sensor (20), and the reference deceleration rate is,A regenerative braking system characterized by a configuration for calculating a reference deceleration (a_ref) by using together a constant acceleration model acceleration value (a_ca) calculated using a constant acceleration model based on the information on relative distance and relative speed and the sensor signals of speed and acceleration, and a CTG policy model acceleration value (a_ctg) calculated using a CTG policy (Constant Time Gap policy, abbreviated as 'CTG policy') model based on the information on relative distance and relative speed and the sensor signals of speed and acceleration. Claim 2 delete Claim 3 In claim 1, the regenerative braking system is characterized by the configuration in which the deceleration necessity determination unit (110) determines whether regenerative braking operation is necessary based on the input value of the accelerator pedal recognition sensor (ASP) among the vehicle sensors (20), and receives information on the relative distance and relative speed between the user vehicle and the vehicle ahead from the front vehicle recognition module (10) to determine whether deceleration of the vehicle is necessary. Claim 4 delete Claim 5 delete Claim 6 A regenerative braking system according to claim 1, characterized in that the constant acceleration model acceleration value (a_ca) is calculated using the following Equation 1 based on information regarding the speed of the user vehicle (v_ego), the speed of the vehicle ahead (v_pre), and the distance (d) between the user vehicle and the vehicle ahead. (Equation 1) Claim 7 A regenerative braking system according to claim 1, characterized in that the CTG policy model acceleration value (a_ctg) is calculated by the following mathematical formula 7. (Mathematical Formula 7) * a_ctg: CTG policy model acceleration value *λ: tuning parameter (the larger the value of λ, the faster the relative distance converges to the safe distance) Claim 8 A regenerative braking system according to claim 1, characterized in that the CTG policy model acceleration value (a_ctg) is calculated by the following mathematical formula 8. (Mathematical formula 8) * a_ctg: CTG policy model acceleration value * v_rei: Relative speed between the user's vehicle and the vehicle ahead Claim 9 A regenerative braking system according to claim 1, characterized in that the reference deceleration rate (a_ref) is calculated by the following mathematical formulas 9 and 10. (Mathematical Formula 9) * w_ca: Weight of the constant acceleration model acceleration value (a_ca) * w_ctg: Weight of the CTG policy model acceleration value (a_ctg) (Equation 10) Claim 10 In a regenerative braking method performed by a front recognition module (10), a vehicle sensor (20), and a control unit (100) installed in a vehicle, the control unit (100) monitors a signal input from an accelerator pedal recognition sensor (APS) of the vehicle sensor (20) (S1); during the monitoring process, the control unit (100) determines whether the value of the sensor signal of the accelerator pedal recognition sensor is less than a preset first reference value and determines whether the user vehicle is accelerating with the accelerator pedal pressed (S2); if the result of the determination in step S2 corresponds to being less than the first reference value and the user vehicle is coasting, the control unit (100) monitors information of the front vehicle input from the front vehicle recognition module (10) (S3), and during the monitoring process determines whether the relative speed between the user vehicle and the front vehicle is less than 0 and determines whether the user vehicle in motion requires deceleration (S4); if the result of the determination in step S4, the user vehicle in motion If the user vehicle requires deceleration, the control unit (100) generates a reference deceleration rate (S5) using information on the vehicle ahead input from the vehicle ahead recognition module (10) and a sensor signal input from the vehicle sensor (20) to maintain the distance from the vehicle ahead within a safe distance; the control unit (100) generates a driving torque command to output a regenerative braking torque that follows the generated reference deceleration rate and transmits it to the vehicle's drive system (200) so that the regenerative braking torque is applied to the vehicle's motor (S6);A regenerative braking method comprising, wherein the step of generating a reference deceleration of the S5 step comprises: the control unit (100) generating a reference deceleration according to the current driving condition of the user vehicle based on information regarding the relative distance and relative speed between the user vehicle and the front vehicle input from the front vehicle recognition module (10) and the speed and acceleration sensor signals of the user vehicle and the front vehicle input from the vehicle sensor (20); and the reference deceleration is characterized by calculating a reference deceleration (a_ref) by using together a constant acceleration model acceleration value (a_ca) calculated using a constant acceleration model based on the information regarding the relative distance and relative speed and the speed and acceleration sensor signals, and a CTG policy model acceleration value (a_ctg) calculated using a CTG policy (Constant Time Gap policy, abbreviated as 'CTG policy') model based on the information regarding the relative distance and relative speed and the speed and acceleration sensor signals.

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