Patent Publication Number: US-2021170877-A1

Title: Method and device for controlling regenerative braking of hybrid commercial vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2019-0162858 filed on Dec. 9, 2019, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     (a) Field of the Disclosure 
     The present disclosure relates to a regenerative braking control apparatus for a hybrid commercial vehicle (or a hybrid electric commercial vehicle), and more particularly, to a method and a device for controlling regenerative braking of a hybrid commercial vehicle capable of performing regenerative braking using an auxiliary brake. 
     (b) Description of the Related Art 
     A demand for an environmentally friendly vehicle is increasing as a demand for improving fuel efficiency of a vehicle is increasing and exhaust gas regulation of each country is strengthened. The environmentally friendly vehicle includes a hybrid vehicle (e.g., a hybrid electric vehicle). A hybrid vehicle is a vehicle that uses two or more power sources, and may be combined in various ways. The power sources include a gasoline engine or a diesel engine using a fossil fuel and a motor driven by electrical energy. 
     The hybrid vehicle includes an engine and a motor, and is driven by a power generated from combust action of the engine and a power generated from rotation of the motor using electrical energy stored in a battery. The hybrid vehicle uses a regenerative braking technology to improve fuel efficiency. In the regenerative braking technology, a part of a braking force of the vehicle is used as electricity generation, the generated electrical energy is charged in the battery, and a part of kinetic energy due to running of the vehicle is used as energy driving a generator of the vehicle. The regenerative braking technology reduces kinetic energy and generates electrical energy. 
     The hybrid vehicle is applied to a commercial vehicle. A hybrid commercial vehicle has a much larger weight than a regular vehicle, and thus a magnitude of an accident and a degree of damage are much greater in an event of an accident of the hybrid commercial vehicle. A weight of a high weight hybrid commercial vehicle is about 140% of weight of the regular vehicle, and thus, a fatal accident of the high weight hybrid commercial vehicle occurs more than the regular vehicle. 
     The hybrid commercial vehicle includes a variety of auxiliary brakes since a main brake such as a foot brake which holds and restrains a wheel of the vehicle does not achieve sufficient braking force. Accordingly, in the hybrid commercial vehicle, a regenerative braking technology using the auxiliary brake is being developed. 
     The above information disclosed in this section is merely for enhancement of understanding of the background of the disclosure, and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     The present disclosure provides a method and a device for controlling regenerative braking of a hybrid commercial vehicle capable of performing regenerative braking using an auxiliary brake. Further, the present disclosure provides the method and the device for controlling regenerative braking of the hybrid commercial vehicle capable of increasing an amount of regenerative braking when the auxiliary brake is operated. 
     An exemplary embodiment of the present disclosure provides a method for controlling regenerative braking of the hybrid commercial vehicle that may include: determining, by a controller, whether a braking request condition of the vehicle is satisfied based on a state data; generating, by the controller, a request braking amount based on the state data when the braking request condition is satisfied; determining, by the controller, whether an operation switch of the auxiliary brake is on; generating, by the controller, an auxiliary braking amount of the auxiliary brake when the operation switch is on; generating, by the controller, a final braking amount based on the request braking amount and the auxiliary braking amount; generating, by the controller, a regenerative braking amount based on the final braking amount; and performing, by the controller, braking of the vehicle based on the final braking amount. 
     The generating of the request braking amount may include: checking, by the controller, a position value of a brake pedal of the vehicle and an acceleration value of the vehicle that are included in the state data when the braking request condition is satisfied; checking, by the controller, a weight of the vehicle based on the acceleration value; and generating, by the controller, the request braking amount based on the position value of the brake pedal and the weight of the vehicle. 
     The generating the auxiliary braking amount may include: checking, by the controller, a braking assistance map including a braking amount for each of a plurality of braking stage numbers included in a braking control lever that adjusts a braking force of the auxiliary brake; checking, by the controller, a braking stage number of the braking control lever; and generating, by the controller, the auxiliary braking amount by extracting a braking amount corresponding to the checked braking stage number from the braking assistance map. 
     The method for controlling regenerative braking of the hybrid commercial vehicle may further include: checking, by the controller, a hydraulic braking amount based on the final braking amount and the regenerative braking amount. The performing of the braking of the vehicle may include: operating, by the controller, the main brake based on the hydraulic braking amount to perform the braking of the vehicle; and performing, by the controller, regenerative braking of the vehicle based on the regenerative braking amount. 
     Additionally, the method for controlling regenerative braking of the hybrid commercial vehicle may include: generating, by the controller, a reference value using the final braking amount and a design coefficient after the braking of the vehicle is performed; checking, by the controller, the hydraulic braking amount of the main brake when the main brake is operated; determining, by the controller, whether the hydraulic braking amount of the main brake is less than or equal to the reference value; and performing, by the controller, the braking of the vehicle using the auxiliary brake when the hydraulic braking amount of the main brake is less than or equal to the reference value. The determining of whether the braking request condition of the vehicle is satisfied based on the state data may include: determining, by the controller, that the braking request condition is satisfied when a position value of a brake pedal of the vehicle included in the state data is greater than or equal to a reference value. 
     An exemplary embodiment of the present disclosure may provide the device for adjusting regenerative braking of the hybrid commercial vehicle, may include: an auxiliary brake configured to assist a braking force of the vehicle; a state detector configured to detect state data for adjusting regenerative braking of the vehicle; and a controller configured to generate a request braking amount using the state data, generate an auxiliary braking amount of the auxiliary brake when an operation switch of the auxiliary brake is on, generate a final braking amount based on the request braking amount and the auxiliary braking amount, generate a regenerative braking amount based on the final braking amount, and perform braking of the vehicle based on the final braking amount. 
     The controller may be configured to check a position value of a brake pedal of the vehicle and an acceleration value of the vehicle that are included in the state data, check a weight of the vehicle based on the acceleration value, and generate the request braking amount based on the position value of the brake pedal and the weight of the vehicle. The controller may be configured to check a braking assistance map including a braking amount for each of a plurality of braking stage numbers included in a braking control lever that adjusts a braking force of the auxiliary brake, check a braking stage number of the braking control lever, and generate the auxiliary braking amount by extracting a braking amount that corresponds to the checked braking stage number from the braking assistance map. 
     The controller may be configured to check a hydraulic braking amount based on the final braking amount and the regenerative braking amount, operate a main brake of the vehicle based on the hydraulic braking amount to perform the braking of the vehicle, and perform regenerative braking of the vehicle based on the regenerative braking amount. The controller may be configured to generate a reference value using the final braking amount and a design coefficient, check the hydraulic braking amount of the main brake when the main brake is operated, and perform the braking of the vehicle using the auxiliary brake when the hydraulic braking amount of the main brake is less than or equal to the reference value. 
     Additionally, the controller may be configured to perform braking of the vehicle through a main brake of the vehicle and the auxiliary brake based on the final braking amount when a regenerative braking stop condition is satisfied. The controller may be configured to determine that the braking request condition of the vehicle is satisfied when a position value of a brake pedal of the vehicle included in the state data is greater than or equal to a reference value. 
     The state detector may include: a brake pedal position detector configured to detect a position value of a brake pedal of the vehicle; a speed detector configured to detect a speed of the vehicle; an acceleration detector configured to detect acceleration of the vehicle; an operation detector configured to detect on or off of the operation switch of the auxiliary brake; and a stage number detector configured to detect a braking stage number of a braking control lever of the auxiliary brake. 
     The method and the device for controlling regenerative braking of the hybrid commercial vehicle according to the exemplary embodiment of the present disclosure may perform the regenerative braking using the auxiliary brake so that the exemplary embodiment of the present disclosure increases the amount of regenerative braking. Further, the exemplary embodiment of the present disclosure may perform braking using the main brake or the auxiliary brake so that the exemplary embodiment of the present disclosure improves braking force and safety of the vehicle. 
     In addition to the aforementioned advantageous effect, an effect that may be obtained or anticipated by applying an exemplary embodiment of the present disclosure will be disclosed explicitly or implicitly in the detailed description of the exemplary embodiment of the present disclosure. In other words, various effects expected by applying an exemplary embodiment of the present disclosure will be disclosed within the detailed description to be provided later. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the disclosure will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a configuration diagram showing a hybrid commercial vehicle to which a method for controlling regenerative braking of the vehicle according to an exemplary embodiment of the present disclosure is applied. 
         FIG. 2  is a block diagram showing a device for controlling regenerative braking of the vehicle according to an exemplary embodiment of the present disclosure. 
         FIG. 3  and  FIG. 4  are flowcharts showing the method of controlling regenerative braking of the vehicle according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. 
     Although exemplary embodiment is described as using a plurality of units to perform the exemplary process, it is understood that the exemplary processes may also be performed by one or plurality of modules. Additionally, it is understood that the term controller/control unit refers to a hardware device that includes a memory and a processor and is specifically programmed to execute the processes described herein. The memory is configured to store the modules and the processor is specifically configured to execute said modules to perform one or more processes which are described further below. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Hereinafter, an operation principle of a method and a device for controlling regenerative braking of a hybrid commercial vehicle of the present disclosure will be described in detail with reference to the description and the accompanying drawings. However, the drawings and the detailed description relate to one exemplary embodiment among several exemplary embodiments for effectively describing features of the present disclosure. Therefore, the present disclosure is not limited only to the drawings and description. 
     Further, in describing below exemplary embodiments of the present disclosure, the related well-known functions or constructions will not be described in detail since they may unnecessarily obscure the understanding of the present disclosure. Further, the following terminologies are defined in consideration of the functions in the present disclosure and may be construed in different ways by the intention of users and operators, practice, or the like. Therefore, the definitions thereof should be construed based on the contents throughout the specification. Further, to effectively describe core technical features of the present disclosure, terms may be appropriately changed, integrated, or separated for those skilled in the art in a technical field to which the present disclosure belongs to explicitly understand the present disclosure, but the present disclosure is not limited thereto. 
     Hereinafter, one exemplary embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a configuration diagram showing a hybrid commercial vehicle to which a method for controlling regenerative braking of the vehicle according to an exemplary embodiment of the present disclosure is applied.  FIG. 1  represents a mild hybrid commercial vehicle included in the hybrid commercial vehicle. The hybrid commercial vehicle (e.g., a hybrid electric commercial vehicle) may include a commercial vehicle including a motor. 
     Referring to  FIG. 1 , the hybrid commercial vehicle may include an engine  110 , an electronic clutch  120 , a transmission  130 , a differential gear device  140 , a driving wheel  145 , a starter-generator or a mild hybrid starter and generator (MHSG)  150 , a first battery  160 , a low voltage DC-DC Converter (LDC)  170 , a second battery  180 , and an electric load  190 . 
     The engine  110  may combust fuel to generate torque. The engine  110  may convert chemical energy into mechanical energy by combusting fuel and air. The engine  110  may include combustion chambers  113 , ignition devices  115 , and injectors  117 . Fuel and air may flow in the combustion chamber  113 , the ignition device  115  may ignite the fuel and the air flowed in the combustion chamber  113 , and the injector  117  may inject fuel into the combustion chamber  113 . For example, the engine  110  may be a gasoline engine, a diesel engine, or a liquefied petroleum injection (LPI) engine. 
     In a power delivery of the hybrid commercial vehicle, torque of the engine  110  may be transmitted to an input shaft  133  of the transmission  130 , and torque output from an output shaft  135  of the transmission  130  may be transmitted to an axle via the differential gear device  140 . When the axle rotates the driving wheel  145 , the hybrid commercial vehicle may be driven by torque of the engine  110 . The electronic clutch  120  may be positioned between engine  110  and the transmission  130 . The electronic clutch  120  may be engaged or released (e.g., disengaged) to transmit or block a torque of the engine  110  to the driving wheel  145 . When the electronic clutch  120  is in an engaged state, a drive shaft of the engine  110  and a drive shaft of the transmission  130  may be connected to transmit the torque of the engine  110  to the driving wheel  145 . When the electronic clutch  120  is in a released state, the drive shaft of the engine  110  and the drive shaft of the transmission  130  may be not connected so that the torque of the engine  110  is not transmitted to the driving wheel  145 . 
     The transmission  130  may be configured to convert an output torque of the engine  110  to a target torque. The transmission  130  may select a shift stage or a transmission stage according to the vehicle speed and a position value of an accelerator pedal of the vehicle to convert a received torque to the target torque, and may be configured to output the converted target torque to the driving wheel  145  to drive the vehicle. The transmission  130  may be an automatic transmission or a manual transmission. 
     The MHSG  150  may be mounted or installed between the engine  110  and the electronic clutch  120 , and may be configured to convert electrical energy to mechanical energy or mechanical energy to electrical energy. In other words, the MHSG  150  may be configured to start the engine  110  or generate electricity by an output of the engine. In addition, the MHSG  150  may be configured to assist the torque of the engine  110 . The hybrid commercial vehicle may use the torque of the MHSG  150  as an auxiliary power while combustion torque of the engine  110  is a main power. 
     It is described that the MHSG  150  is disposed between the engine  110  and the electronic clutch  120 , but the present disclosure is not limited thereto. For example, the MHSG  150  may be connected to the engine  110  via a belt at a front end of the engine  110 , may be positioned between the electronic clutch  120  and the transmission  130 , may be positioned behind the transmission  130 , or may be positioned between the differential gear device  140  and the driving wheel  145 . 
     The first battery  160  may be configured to supply electric power to the MHSG  150  or may be charged by electric power collected using the MHSG  150 . The first battery  160  may be a high voltage battery and may be referred to as a main battery. For example, the first battery  160  may be a lithium-ion battery. The lithium-ion battery may have rapid charging and discharging speed and good durability, but may have poor energy storage performance and poor charging and discharging efficiency at an extremely low temperature. 
     The LDC  170  may be configured to convert a voltage (e.g., about 48 V) supplied from the first battery  160  to a low voltage (e.g., about 12 V) to charge the second battery  180 . The second battery  180  may be charged through electric power supplied from the LDC  170 . The second battery  180  may be a low voltage battery and may be called an auxiliary battery. The second battery  180  may be configured to supply electric power to the electric load  190  using low voltage. For example, the second battery  180  may be an absorptive glass mat (AGM) battery or a lead-acid battery. The electric load  190  may represent a part driven by the second battery  180 . For example, the electric load  190  may include a headlight, a fog light, a wiper, and an air conditioner. 
       FIG. 2  is a block diagram showing a device for controlling regenerative braking of the vehicle according to an exemplary embodiment of the present disclosure. Referring to  FIG. 2 , the device for controlling regenerative braking of the hybrid commercial vehicle may include a state detector  210 , a controller  250 , the MHSG  150 , a main brake  260 , and an auxiliary brake  270 . 
     The state detector  210  may be configured to detect state data for adjusting regenerative braking of the vehicle. The state detector  210  may include a brake pedal position detector  221 , an accelerator pedal position detector  223 , a speed detector  225 , an acceleration detector  227 , an operation detector  229 , and a stage number detector  231 . The brake pedal position detector  221  may be configured to detect a degree to which a driver of the vehicle engages a brake pedal of the vehicle (e.g., amount of force exerted onto the pedal). The brake pedal position detector  221  may be configured to detect a position value of the brake pedal (i.e., a degree to which the brake pedal is engaged) to provide a signal corresponding to the detected value to the controller  250 . 
     A position value of the brake pedal may be 100% when the brake pedal is fully engaged, and the position value of the brake pedal may be 0% when the brake pedal is disengaged. The accelerator pedal position detector  223  may be configured to detect a degree to which the driver engages an accelerator pedal of the vehicle. The accelerator pedal position detector  223  may be configured to detect a position value of the accelerator pedal (i.e., a degree to which the accelerator pedal is engaged) to provide a signal corresponding to the detected value to the controller  250 . A position value of the accelerator pedal may be 100% when the accelerator pedal is fully engaged, and the position value of the accelerator pedal may be 0% when the accelerator pedal is disengaged. 
     In another exemplary embodiment of the present disclosure, a throttle valve opening detector mounted on an intake passage of the vehicle may be used instead of the accelerator pedal position detector  223 . The accelerator pedal position detector  223  may include the throttle valve opening detector. The speed detector  225  may be configured to detect a speed of the hybrid commercial vehicle and may provide the vehicle speed to the controller  250 . The speed detector  225  may be installed at the driving wheel  140  of the hybrid commercial vehicle. 
     The acceleration detector  227  may be configured to detect acceleration of the hybrid commercial vehicle. The acceleration detector  227  may be configured to transmit the detected acceleration to the controller  250 . When the acceleration detector  227  is not included in the state detector  210 , the controller  250  may be configured to calculate the vehicle acceleration by differentiating the vehicle speed detected by the speed detector  225 . 
     The operation detector  229  may be configured to detect on or off of an operation switch that operates the auxiliary brake  270  and may be configured to transmit the detected on or off of the operation switch to the controller  250 . When the driver turns on the operation switch for operation of the auxiliary brake  270 , the operation detector  229  may be configured to detect an on-state of the operation switch and transmit a detection signal corresponding to the on-state to the controller  250 . 
     The stage number detector  231  may be configured to detect a number of a stage of braking of a braking control lever in the vehicle. The braking control lever may be a lever for receiving the stage number of braking corresponding to a braking force of the auxiliary brake  270  from the driver. The braking control lever may include a plurality of braking stage numbers. The stage number detector  231  may provide the detected number of braking stage to the controller  250 . 
     The controller  250  may be configured to operate the state detector  210 , the MHSG  150 , the main brake  260 , and the auxiliary brake  270  to adjust regenerative braking. The controller  250  may be configured to receive the state data from the state detector  210 . The controller  250  may be configured to determine whether a braking request condition of the vehicle is satisfied based on the state data. The braking request condition may indicate a condition for determining whether the driver requests braking of the hybrid commercial vehicle. 
     When the braking request condition is satisfied, the controller  250  may be configured to generate a request braking amount based on the state data. The controller  250  may be configured to generate an auxiliary braking amount of the auxiliary brake  270  when the operation switch of the auxiliary brake  270  is in an on state. Additionally, the controller  250  may be configured to generate a final braking amount based on the request braking amount and the auxiliary braking amount. The controller  250  may be configured to generate a regenerative braking amount based on the final braking amount, and generate a hydraulic braking amount or a hydraulic pressure braking amount based on the final braking amount and the regenerative braking amount. 
     Further, the controller  250  may be configured to operate the MHSG  150  based on the regenerative braking amount to perform regenerative braking. The controller  250  may be configured to operate the main brake  260  based on the hydraulic braking amount to perform braking of the vehicle. The controller  250  may include a battery controller (e.g., a battery management system), a motor controller, an engine controller, a transmission controller, and a brake controller (e.g., an electric brake system), but the present disclosure is not limited thereto. 
     The controller  250  may be implemented as at least one microprocessor operated by a program. The program may include a series of commands for executing the method for controlling regenerative braking of the hybrid commercial vehicle according to the exemplary embodiment of the present disclosure described below. The MHSG  150  may be configured to perform regenerative braking under an operation of the controller  250  to supply electric power to the first battery  160 . The main brake  260  may be configured to provide braking hydraulic pressure to the driving wheel  140  under an operation of the controller  250  to perform braking of the hybrid commercial vehicle. 
     The auxiliary brake  270  may be configured to assist a braking force of the vehicle. In other words, the auxiliary brake  270  may be configured to assist an operation of the main brake  260  according to an operation of the controller  250 . The auxiliary brake  270  may include an exhaust brake, an engine brake, a Jake brake, an intarder, or a retarder. 
     The method for controlling regenerative braking of the hybrid commercial vehicle will be described in more detail referring to  FIG. 3  and  FIG. 4 .  FIGS. 3 and 4  are flowcharts showing the method of controlling regenerative braking of the vehicle according to an exemplary embodiment of the present disclosure. Referring to  FIG. 3 , the controller  250  may be configured to determine whether the braking request condition is satisfied based on the state data in step S 310 . 
     In particular, the controller  250  may be configured to receive a brake pedal position value from the brake pedal position detector  221  of the state detector  210 . The controller  250  may be configured to determine whether the position value of the brake pedal is greater than or equal to a first reference value so that the controller determines whether the braking request condition is satisfied. The first reference value may represent a value for determining whether braking of the vehicle is requested based on the brake pedal, and may be preset. 
     The controller  250  may be configured to check a position value of the accelerator pedal. The controller  250  may be configured to receive the position value of the accelerator pedal from the accelerator pedal position detector  223 . Additionally, the controller  250  may be configured to determine whether the position value of the accelerator pedal is less than or equal to a second reference value. The second reference value may be a value for determining whether the accelerator pedal is off, and may be set in advance. For example, the second reference value may be 0. 
     When the braking request condition is not satisfied, the controller  250  may be configured to again monitor the state data to determine whether the braking request condition is satisfied. When the braking request condition is satisfied, the controller  250  may be configured to generate or calculate a request braking amount based on the state data in step S 320 . When the position value of the brake pedal is greater than or equal to the first reference value and the position value of the accelerator pedal is less than or equal to the second reference value, the controller  250  may be configured to check the position value of the brake pedal. 
     The controller  250  may be configured to receive an acceleration value of the vehicle from the acceleration detector  227  of the state detector  210 . The controller  250  may be configured to check a weight of the hybrid commercial vehicle based on the acceleration value. The controller  250  may be configured to generate the request braking amount based on the position value of the brake pedal and the weight of the vehicle. In particular, the controller  250  may be configured to check a control map including braking amounts according to a plurality of brake pedal position values and a plurality of weights of the vehicle. The control map may be a map table or a memory. The controller  250  may be configured to generate the request braking amount by extracting the braking amount based on the position value of the brake pedal and the weight of the vehicle from the control map. 
     Additionally, the controller  250  may be configured to determine whether the operation switch of the auxiliary brake  270  is in an on state in step S 330 . The controller  250  may be configured to receive the detection signal from the operation detector  229  of the state detector  210 , and determine whether the operation switch is on based on the detection signal. When the operation switch is on, the controller  250  may be configured to generate the auxiliary braking amount of the auxiliary brake  270  in step S 340 . 
     Particularly, the controller  250  may be configured to check a braking assistance map including a braking amount for each of a plurality of the braking stage numbers. The braking assistance map may be a map table or a memory. The braking amount may be a maximum allowable braking amount in the auxiliary brake  270 . The braking assistance map may be set in advance or may be reset through learning. 
     The controller  250  may be configured to receive a braking stage number engaged in the braking control lever from the stage number detector  231  of the state detector  210 . The controller  250  may be configured to generate the auxiliary braking amount by extracting a braking amount corresponding to a braking stage number detected by the stage number detector  231  from the braking assistance map. In addition, the controller  250  may be configured to generate the final braking amount based on the request braking amount and the auxiliary braking amount in step S 350 . For example, the controller  250  may be configured to generate the final braking amount by adding the auxiliary braking amount to the request braking amount. 
     The controller  250  may be configured to generate the request braking amount as the final braking amount when the operation switch of the auxiliary brake  270  is in an off state. The controller  250  may be configured to determine whether a regenerative braking stop condition is satisfied in step S 360 . The regenerative braking stop condition may include a condition in which an operation for stopping regenerative braking is requested during shifting of the transmission  130  or a failure of the MENG  150  that is a regenerative braking system. 
     In the step S 360  the controller may be configured to determine that the regenerative braking stop condition is satisfied after the final braking amount is generated, but the present disclosure is not limited thereto. In another exemplary embodiment of the present disclosure, the controller  250  may be configured to determine whether the regenerative braking stop condition is satisfied immediately after the step S 320 . The controller  250  may be configured to perform braking of the vehicle using the main brake  260  and the auxiliary brake  270  when the regenerative braking stop condition is satisfied in step S 370 . In particular, when the regenerative braking stop condition is satisfied, the controller  250  may be configured to stop regenerative braking, and perform braking of the vehicle through the main brake  260  and the auxiliary brake  270  based on the final braking amount. 
     Further, the controller  250  may be configured to generate the regenerative braking amount based on the final braking amount when the regenerative braking stop condition is not satisfied in step S 380 . In particular, the controller  250  may be configured to generate a regenerative braking available amount based on a shifting state of the transmission  130 , a charging state of the first battery  160 , a state of the starter-generator  150 , an altitude of a road that the vehicle drives on, or an altitude of a downhill road that the vehicle is being driven on, and generate the regenerative braking amount based on the final braking quantity and the regenerative braking available amount. 
     The controller  250  may be configured to generate the hydraulic braking amount based on the final braking amount and the regenerative braking amount in step S 410 . For example, the controller  250  may be configured to generate the hydraulic braking amount by subtracting the regenerative braking amount from the final braking amount. The controller  250  may be configured to perform regenerative braking based on the regenerative braking amount, and perform braking of the vehicle based on the hydraulic braking amount in step S 420 . 
     Particularly, the controller  250  may be configured to generate a regenerative braking torque according to the regenerative braking amount, generate a motor torque according to the regenerative braking torque, and operate the MHSG  150  based on the motor torque to perform the regenerative braking. The controller  250  may be configured to adjust the hydraulic pressure supplied to a brake cylinder included in the main brake  260  based on the hydraulic braking amount to perform the braking of the hybrid commercial vehicle. The controller  250  may then be configured to check the hydraulic braking amount of the main brake  260  when the main brake is operated in step S 430 . 
     The controller  250  may be configured to determine whether the hydraulic braking amount of the main brake  260  is less than or equal to a reference value or a threshold value in step S 440 . In particular, the controller  250  may be configured to generate the reference value using the final braking amount and a design coefficient. The controller  250  may be configured to generate the reference value by multiplying the final braking amount by the design coefficient. The design coefficient is a coefficient designed to check a braking force of the main brake  260 , and may be set through a test. For example, the design coefficient may be 0.98. The controller  250  may be configured to determine whether the hydraulic braking amount of the main brake  260  is less than or equal to the reference value to determine whether the braking force of the main brake  260  is insufficient. 
     Additionally, the controller  250  may be configured to perform braking of the vehicle through the auxiliary brake  270  when the hydraulic braking amount of the main brake  260  is less than or equal to the reference value in step S 450 . In particular, the controller  250  does not secure a sufficient braking force of the vehicle from the main brake  260  when the hydraulic braking amount of the main brake  260  is less than or equal to the reference value. Therefore, the controller  250  may be configured to operate the auxiliary brake  270  to provide an additional braking force to the vehicle. The controller  250  may be configured to perform braking of the vehicle through the auxiliary brake  270  based on the auxiliary braking amount. The controller  250  may be configured to check an auxiliary braking amount performed by the auxiliary brake  270 . The controller  250  may then be configured to reset the braking assistance map based on the auxiliary braking amount performed by the auxiliary brake  270  and the braking stage number of the braking control lever. Since the braking assistance map is reset, the braking amount of the auxiliary brake  270  may be determined more accurately. 
     The method of controlling regenerative braking for the hybrid commercial vehicle according to the exemplary embodiment of the present disclosure may perform regenerative braking by including the auxiliary braking amount of the auxiliary brake  170  in the regenerative braking amount when the auxiliary brake  170  is operated by the driver. Thus, an amount of the regenerative braking may be increased compared to a case where regenerative braking is performed in an existing vehicle. 
     While this disclosure has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     DESCRIPTION OF SYMBOLS 
     
         
         
           
               110 : engine 
               120 : electronic clutch 
               130 : transmission 
               140 : differential gear device 
               145 : driving wheel 
               150 : MHSG 
               160 : first battery 
               170 : LDC 
               180 : second battery 
               190 : electric load 
               210 : state detector 
               250 : controller 
               260 : main brake 
               270 : auxiliary brake