A cooperative braking system and control method for an in-wheel motor and a small EMB

Abstract

The application relates to a collaborative braking system and control method of a wheel hub motor and a small EMB, and belongs to the field of automobile control technology.In the collaborative braking system of the wheel hub motor and the small EMB, a wheel hub motor control system is connected in series by a power battery, an energy consumption adjustable resistor, a motor controller and a wheel hub motor, and the wheel hub motor is fixed to the wheel hub of a wheel; a small EMB control system is connected in series by a power battery, a small EMB, an EMB controller and a DC / DC converter, and the small EMB is fixed to the wheel hub of a wheel; and the application further proposes a collaborative braking control method based on the collaborative braking system, so that the braking potential of the wheel hub motor is exerted as much as possible, the braking energy is fully recovered, and the energy originally dissipated by the EMB is as much as possible to be borne to realize vehicle braking, so that the design size of the EMB is reduced, the energy utilization effect can be improved while meeting the wheel edge arrangement requirement.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of automobile control, and particularly relates to a collaborative braking system and control method of an in-wheel motor and a small EMB. BACKGROUND

[0002] Under the general trend of intelligent driving and intelligent chassis development, the chassis distributed drive braking system of an in-wheel motor (IWM) + an electronic mechanical brake system (EMB) has a good application prospect and gradually becomes a research hotspot of enterprises and colleges due to its characteristics of "flexible layout, good compatibility of architecture, and good control integration", but for passenger cars, the wheel edge space is limited, especially when an in-wheel motor is used as a drive motor, the wheel edge size is more nervous, therefore, if the EMB structure is still designed according to the braking capacity of the traditional hydraulic system, the size of the EMB will be large, which greatly increases the layout difficulty and the heat dissipation risk, especially the front wheel needs a larger size and even leads to the failure of layout, and the momentum consumed by the EMB braking is completely dissipated in the form of friction heat and cannot be recycled, at the same time, the EMB itself also needs to dissipate additional energy, therefore, if the braking potential of the in-wheel motor can be exerted as much as possible, the braking energy can be fully recycled, and the energy that is originally dissipated by the EMB can be as much as possible to realize the braking of the vehicle, the size of the EMB can be reduced, and the energy utilization effect can be improved while meeting the wheel edge layout requirement. SUMMARY

[0003] The application aims to provide a collaborative braking system and control method of an in-wheel motor and a small EMB, which can exert the braking potential of the in-wheel motor as much as possible, reduce the size of the EMB, and realize the wheel edge layout requirement while improving the energy utilization effect.

[0004] The collaborative braking system of an in-wheel motor and a small EMB of the application is composed of an in-wheel motor control system A, a small EMB control system B, and a power battery 1, and the power battery 1 is shared by the in-wheel motor control system A and the small EMB control system B.

[0005] The in-wheel motor system A is composed of the power battery 1, an energy consumption adjustable resistor 2, a motor controller 3, and an in-wheel motor 4, and the power battery 1, the energy consumption adjustable resistor 2, the motor controller 3, and the in-wheel motor 4 are arranged in sequence from front to back and connected in series, the power battery 1 is connected with the front end of the energy consumption adjustable resistor 2 through a direct current bus, the rear end of the energy consumption adjustable resistor 2 is connected with the front end of the motor controller 3 through a direct current bus, and the rear end of the motor controller 3 is connected with the in-wheel motor 4 through a three-phase alternating current bus.

[0006] The small EMB control system B is composed of the power battery 1, the small EMB 6, the EMB controller 7 and the DC / DC converter 8, the power battery 1, the DC / DC converter 8, the EMB controller 7 and the small EMB 6 are arranged in sequence from left to right and connected in series, the power battery 1 is connected with the left end of the DC / DC converter 8 through a DC bus, the right end of the DC / DC converter 8 is connected with the left end of the EMB controller 7 through a DC bus, and the right end of the EMB controller 7 is connected with the small EMB 6 through a three-phase AC bus. The hub motor 4 of the hub motor control system A is fixed to the hub of the wheel 5; the small EMB 6 of the small EMB control system B is fixed to the hub of the wheel 5.

[0007] The control method of the cooperative braking of the hub motor and the small EMB comprises the following steps:

[0008] 1) setting the cooperative braking system of the hub motor and the small EMB;

[0009] 2) the working mode of the hub motor control system A comprises a motor driving mode and a motor braking mode, and specifically:

[0010] 2.1 motor driving mode: the power battery 1 outputs high-voltage direct current through a DC bus, flows to the motor controller 3 through the energy consumption adjustable resistor 2, the motor controller 3 converts two-phase direct current into three-phase alternating current and outputs to the hub motor 4 for driving torque control, the hub motor 4 drives the wheel 5 to rotate, at this time, in order to reduce the output loss, the resistance value of the energy consumption adjustable resistor 2 is adjusted to 0;

[0011] 2.2 motor braking mode: negative torque current is required for motor braking, according to different sources of negative torque current, the motor braking mode comprises motor regenerative braking, energy consumption braking and motor power consumption braking, and specifically:

[0012] 2.2.1 when the motor regenerative braking is in the motor regenerative braking, the negative torque current comes from the hub motor 4 and finally flows to the power battery 1, at this time, the kinetic energy of the rotating wheel 5 drives the rotor of the hub motor 4 to rotate, according to the Faraday's law of electromagnetic induction, when the rotor rotates, the stator coil will induce a counter electromotive force, the motor controller 3 adjusts the working state of the internal IGBT to make the electronic stator coil generate negative torque current to realize braking, and the negative torque current flows through the energy consumption adjustable resistor 2 to charge the power battery 1, at this time, in order to improve the energy recovery effect, the energy consumption adjustable resistor 2 is adjusted to 0;

[0013] 2.2.2 When in energy-consuming braking, negative torque current comes from the wheel hub motor 4, and finally flows to the energy-consuming adjustable resistor 2. At this time, the kinetic energy of the rotating wheel 5 drives the rotor of the wheel hub motor 4 to rotate. According to Faraday's law of electromagnetic induction, when the rotor rotates, an induced electromotive force will be induced in the stator coil. The motor controller 3 adjusts the working state of the internal IGBT to make the induced electromotive force generated by the motor stator coil act on the energy-consuming adjustable resistor 2, and generates negative torque current to realize braking. By adjusting the resistance value of the energy-consuming adjustable resistor 2, the kinetic energy of the wheel hub motor 4 is completely converted into heat energy dissipated by the resistor. However, at this time, although braking is achieved, the kinetic energy cannot be recovered. Energy-consuming braking and motor regenerative braking can be performed simultaneously. From the perspective of improving energy utilization, motor regenerative braking is normally used as the main braking mode. When motor regenerative braking cannot meet the braking demand, energy-consuming braking is used to supplement it. When motor regenerative braking cannot be performed, energy-consuming braking is used;

[0014] 2.2.3 When in motor power-consuming braking, negative current comes from the power battery 1. At this time, the motor controller 3 adjusts the working state of the internal IGBT to make the motor stator generate negative current, so that the motor generates braking torque to realize braking. The wheel hub motor 4 needs to consume electric energy to brake and cannot recover the braking energy. Power-consuming braking cannot be performed simultaneously with the other two braking modes.

[0015] 3) The working mode of the small EMB control system B is EMB friction braking:

[0016] The power battery 1 outputs high-voltage direct current through the DC bus, which is converted into low-voltage direct current by the DC / DC converter 8 and input to the EMB controller 7. The EMB controller 7 converts two-phase direct current into three-phase alternating current and outputs it to the small EMB 6 for braking torque control.

[0017] The small EMB 6 is installed in the hub of the wheel 5 and provides braking torque for the wheel 5 to realize vehicle braking. Therefore, when the small EMB 6 is used for vehicle braking, the power battery 1 needs to provide additional electric energy to drive the small EMB 6 to work. In addition, the energy dissipated by the small EMB 6 friction braking cannot be recovered.

[0018] 4) The braking mode judgment includes the following steps:

[0019] 4.1 Determine whether the vehicle speed is less than 5 km / h. If yes, directly perform motor power-consuming braking;

[0020] 4.2 Otherwise, continue to determine whether the current SOC of the power battery 1 is less than 90%. If yes, continue to determine whether the current total required braking torque is less than the current maximum motor regenerative torque. If less, perform motor regenerative braking;

[0021] 4.3 Otherwise, continue to determine whether the current hub motor 4 is in the constant power zone, if yes, continue to determine whether the current total demand braking torque is less than the sum of the maximum motor regenerative braking torque and the maximum energy consumption braking torque, if yes, carry out motor regenerative braking and energy consumption braking at the same time, adjust the resistance value of the energy consumption adjustable resistor 2, so that the hub motor 4 provides the maximum regenerative braking torque that can be provided at present, and the remaining braking torque is provided by energy consumption braking;

[0022] 4.4 Otherwise, it is indicated that the maximum motor regenerative braking torque and the maximum energy consumption braking torque still cannot meet the braking demand, at this time, motor regenerative braking, energy consumption braking and EMB friction braking are carried out at the same time, the hub motor 4 provides the maximum regenerative braking torque that can be provided at present, the resistance value of the energy consumption adjustable resistor 2 is adjusted to the upper limit to provide the maximum energy consumption braking torque, and the remaining demand braking torque is provided by EMB friction braking; the energy consumption adjustable resistor 2

[0023] 4.5 If the current motor is in the constant torque zone, in order to ensure the maximum energy recovery effect, the energy consumption resistor resistance value is adjusted to 0, at this time, motor regenerative braking and EMB friction braking are carried out, the hub motor 4 provides the maximum regenerative braking torque that can be provided at present, and the remaining demand braking torque is provided by EMB friction braking;

[0024] 4.6 If the SOC of the current power battery 1 is greater than 90%, at this time, the motor kinetic energy cannot be recovered to charge the power battery 1, that is, motor regenerative braking cannot be carried out, continue to determine whether the current total demand braking torque is less than the maximum energy consumption braking torque, if yes, carry out energy consumption braking directly;

[0025] 4.7 Otherwise, energy consumption braking and EMB friction braking are carried out at the same time, the energy consumption resistor resistance value is adjusted to the upper limit to provide the maximum energy consumption braking torque, and the remaining demand braking torque is provided by EMB friction braking.

[0026] The beneficial effects of the application are that the application can fully develop the braking potential of the hub motor, fully recover the braking energy, and can bear the energy originally dissipated by the EMB to realize vehicle braking, can reduce the braking demand on the EMB, reduce the size of the EMB, and also can reduce the energy consumption of the EMB itself, realize the satisfaction of the wheel edge arrangement demand while improving the energy utilization effect. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a structural schematic diagram of a collaborative braking system of a hub motor and a small EMB;

[0028] Figure 2 is a flow chart of a collaborative braking control method of a hub motor and a small EMB;

[0029] Among them: A. Hub motor control system B. Small EMB control system 1. Power battery 2. Energy consumption adjustable resistor 3. Motor controller 4. Hub motor 5. Wheel 6. Small EMB 7. EMB controller 8. DC / DC converter. Detailed Implementation

[0030] The present invention will now be described in conjunction with the accompanying drawings.

[0031] like Figure 1 As shown, the present invention provides a coordinated braking system of a hub motor and a small EMB, which consists of a hub motor control system A, a small EMB control system B, and a power battery 1. The power battery 1 is shared by the hub motor control system A and the small EMB control system B.

[0032] The hub motor system A consists of a power battery 1, an adjustable energy-consuming resistor 2, a motor controller 3, and a hub motor 4. The power battery 1, the adjustable energy-consuming resistor 2, the motor controller 3, and the hub motor 4 are arranged sequentially from front to back and connected in series. The power battery 1 is connected to the front end of the adjustable energy-consuming resistor 2 via a DC bus. The rear end of the adjustable energy-consuming resistor 2 is connected to the front end of the motor controller 3 via a DC bus. The rear end of the motor controller 3 is connected to the hub motor 4 via a three-phase AC bus.

[0033] The small EMB control system B consists of a power battery 1, a small EMB 6, an EMB controller 7, and a DC / DC converter 8. The power battery 1, DC / DC converter 8, EMB controller 7, and small EMB 6 are arranged sequentially from left to right and connected in series. The power battery 1 is connected to the left end of the DC / DC converter 8 via a DC bus. The right end of the DC / DC converter 8 is connected to the left end of the EMB controller 7 via a DC bus. The right end of the EMB controller 7 is connected to the small EMB 6 via a three-phase AC bus. The hub motor 4 of the hub motor control system A is fixed to the hub of the wheel 5; the small EMB 6 of the small EMB control system B is fixed to the hub of the wheel 5.

[0034] like Figure 2 As shown, the present invention discloses a control method for coordinated braking based on a hub motor and a small EMB, which can leverage the braking potential of the hub motor and small EMB coordinated braking system, achieving the goal of reducing EMB size and simplifying wheel-side arrangement while ensuring vehicle braking safety and energy recovery effect. The method includes the following steps:

[0035] 1) Install a coordinated braking system of hub motor and small EMB;

[0036] 2) The working modes of the hub motor control system A include motor drive mode and motor braking mode, specifically:

[0037] 2.1 Motor driving mode: the power battery 1 outputs high-voltage direct current through the direct current bus, flows to the motor controller 3 through the energy consumption adjustable resistor 2, the motor controller 3 converts two-phase direct current into three-phase alternating current and outputs to the wheel hub motor 4 for driving torque control, the wheel hub motor 4 drives the wheel 5 to rotate, at this time, in order to reduce the output loss, the resistance value of the energy consumption adjustable resistor 2 is adjusted to 0;

[0038] 2.2 Motor braking mode: negative torque current is required for motor braking, according to different sources of negative torque current, the motor braking mode includes: motor regenerative braking, energy consumption braking and motor power consumption braking, specifically:

[0039] 2.2.1 When in motor regenerative braking, the negative torque current comes from the wheel hub motor 4 and finally flows to the power battery 1, at this time, the kinetic energy of the rotating wheel 5 drives the rotor of the wheel hub motor 4 to rotate, according to Faraday's law of electromagnetic induction, when the rotor rotates, the stator coil will induce a counter electromotive force, the motor controller 3 adjusts the working state of the internal IGBT to make the electronic stator coil generate negative torque current to realize braking, and the negative torque current flows through the energy consumption adjustable resistor 2 to charge the power battery 1, at this time, in order to improve the energy recovery effect, the energy consumption adjustable resistor 2 is adjusted to 0;

[0040] 2.2.2 When in energy consumption braking, the negative torque current comes from the wheel hub motor 4 and finally flows to the energy consumption adjustable resistor 2, at this time, the kinetic energy of the rotating wheel 5 drives the rotor of the wheel hub motor 4 to rotate, according to Faraday's law of electromagnetic induction, when the rotor rotates, the stator coil will induce a counter electromotive force, the motor controller 3 adjusts the working state of the internal IGBT to make the counter electromotive force generated by the motor stator coil act on the energy consumption adjustable resistor 2, to generate negative torque current to realize braking, by adjusting the resistance value of the energy consumption adjustable resistor 2, the kinetic energy of the wheel hub motor 4 is completely converted into heat energy dissipated by the resistor, however, at this time, although braking is achieved, the kinetic energy cannot be recovered; energy consumption braking and motor regenerative braking can be performed at the same time, from the perspective of improving energy utilization, motor regenerative braking is normally used as the main mode; when motor regenerative braking cannot meet the braking demand, energy consumption braking is used to supplement, or when motor regenerative braking cannot be performed, energy consumption braking is performed;

[0041] 2.2.3 When in motor power consumption braking, the negative current comes from the power battery 1, at this time, the motor controller 3 adjusts the working state of the internal IGBT to make the motor stator generate negative current, so that the motor generates braking torque to realize braking, the wheel hub motor 4 needs to consume electric energy to brake, and the braking energy cannot be recovered, motor power consumption braking cannot be performed at the same time as the other two braking modes when the motor speed is too low or the battery is fully charged and cannot charge the battery;

[0042] 3) The working mode of the small EMB control system B is EMB friction braking:

[0043] The power battery 1 outputs high-voltage direct current through the direct current bus, is converted into low-voltage direct current through the DC / DC converter 8, and is input to the EMB controller 7, and the EMB controller 7 converts two-phase direct current into three-phase alternating current and outputs the three-phase alternating current to the small EMB 6 to control the braking torque;

[0044] The small EMB 6 is installed in the hub of the wheel 5 and provides braking torque for the wheel 5 to brake the vehicle, and therefore, when the vehicle is braked by using the small EMB 6, the power battery 1 needs to additionally provide electric energy to drive the small EMB 6 to work, and in addition, the energy dissipated by the friction braking of the small EMB 6 cannot be recovered.

[0045] The adjustable energy consumption resistor 2 is used in the hub motor control system A to realize energy consumption braking, and the energy consumption principle is consistent with the friction braking of the EMB in the small EMB control system B, and both are to dissipate kinetic energy in the form of heat, and therefore, the energy consumption braking can bear as much energy as possible that is originally dissipated by the EMB to brake the vehicle, and at this time, the braking capacity requirement of the EMB is reduced, the size of the EMB can be reduced, the pressure of the wheel edge arrangement is relieved, in addition, the EMB friction braking needs to additionally consume the battery electric energy to drive the EMB to work, and the energy consumption resistor 2 does not need to, and therefore, the energy consumption braking can also better improve the energy utilization effect, and reduce the braking requirement of the EMB, and the design size of the EMB can be reduced.

[0046] 4) The braking mode determining includes the following steps:

[0047] 4.1 It is judged whether the vehicle speed is less than 5 km / h, and if yes, the motor energy consumption braking is directly performed;

[0048] The reason is that at this time, the motor speed is low, the back electromotive force generated is low, the negative torque current is low, and sufficient braking torque cannot be generated, and therefore, the motor regenerative braking or energy consumption braking cannot be used.

[0049] 4.2 Otherwise, it is continuously judged whether the SOC of the current power battery 1 is less than 90%, and if yes, it is continuously judged whether the current total required braking torque is less than the current maximum regenerative torque of the motor, and if yes, the motor regenerative braking is performed;

[0050] The reason is that at this time, the motor regenerative braking has the ability to bear all braking requirements, and the motor regenerative braking is preferentially used to improve the energy recovery effect;

[0051] 4.3 Otherwise, continue to determine whether the current hub motor 4 is in the constant power zone, if so, continue to determine whether the current total demand braking torque is less than the sum of the current motor maximum regenerative braking torque and the maximum energy consumption braking torque, if so, the motor regenerative braking and energy consumption braking are performed at the same time, the resistance value of the energy consumption adjustable resistor 2 is adjusted, so that the hub motor 4 provides the maximum regenerative braking torque that can be provided at present, and the remaining braking torque is provided by the energy consumption braking;

[0052] The reason is that when the motor is in the constant power zone, at this time the motor speed is high, the back electromotive force generated is greater than the battery charging voltage, and direct charging of the battery will increase the load of the battery and even damage the battery. Therefore, when the demand braking torque is less than the sum of the current motor maximum regenerative braking torque and the maximum energy consumption braking torque, a part of the back electromotive force is consumed by the energy consumption resistor, and the remaining back electromotive force just meets the battery charging requirement, so that the motor provides the maximum regenerative braking torque that can be provided at present, and the remaining braking torque is provided by the energy consumption braking;

[0053] 4.4 Otherwise, it is indicated that the motor maximum regenerative braking torque and the maximum energy consumption braking torque still cannot meet the braking demand, at this time the motor regenerative braking, energy consumption braking and EMB friction braking are performed at the same time, the hub motor 4 provides the maximum regenerative braking torque that can be provided at present, the resistance value of the energy consumption adjustable resistor 2 is adjusted to the upper limit to provide the maximum energy consumption braking torque, and the remaining demand braking torque is provided by the EMB friction braking; The reason is that at this time the vehicle braking demand is large, so that the motor regenerative braking and energy consumption braking cannot meet the demand even when they work at the same time, and the EMB friction braking is supplemented;

[0054] 4.5 If the current motor is in the constant torque zone, in order to ensure the maximum energy recovery effect, the resistance value of the energy consumption resistor is adjusted to 0, at this time the motor regenerative braking and the EMB friction braking are performed, the hub motor 4 provides the maximum regenerative braking torque that can be provided at present, and the remaining demand braking torque is provided by the EMB friction braking; When the motor is in the constant torque zone, at this time the motor speed is low, and the back electromotive force generated is even lower than the battery charging voltage, at this time all the back electromotive force is used for charging the battery, and no additional consumption of the energy consumption resistor is needed. Therefore, in order to improve the energy recovery effect, the energy consumption braking is no longer involved, and therefore when the demand braking torque is greater than the current motor maximum regenerative braking torque, the motor regenerative braking and the EMB friction braking are performed, the motor provides the maximum regenerative braking torque that can be provided at present, and the remaining demand braking torque is supplemented by the EMB friction braking;

[0055] 4.6 If the SOC of the current power battery 1 is greater than 90%, the motor kinetic energy cannot be recovered to charge the power battery 1 at this time, that is, the motor regenerative braking cannot be performed, and it is continuously determined whether the current total demand braking torque is less than the maximum energy consumption braking torque. If yes, the energy consumption braking is directly performed; the reason is that the battery power is too high at this time, and the battery cannot be continuously charged, so the motor regenerative braking cannot be performed. At this time, the energy consumption braking is preferentially selected for the energy consumption braking and the motor energy consumption braking because the motor energy consumption braking needs additional battery output power, which reduces the energy utilization effect. Therefore, when it is determined whether the total demand braking torque is less than the maximum energy consumption braking torque, the energy consumption braking is performed;

[0056] 4.7 Otherwise, the energy consumption braking and the EMB friction braking are simultaneously performed, the energy consumption resistance value is adjusted to the upper limit, the maximum energy consumption braking torque is provided, and the remaining demand braking torque is provided by the EMB friction braking; the reason is that the energy consumption braking cannot meet the braking demand at this time, and the EMB friction braking is supplemented.

Claims

1. A control method for cooperative braking based on a hub motor and a small EMB, characterized by Comprising the following steps: 1) Set the hub motor and small EMB cooperative braking system: The hub motor and small EMB cooperative braking system is composed of hub motor control system (A), small EMB control system (B) and Power battery (1) is shared by hub motor control system (A) and small EMB control system (B); Hub motor control system (A) is composed of power battery (1), energy consumption adjustable resistance (2), motor controller (3) and hub motor (4), which are arranged in order from front to back and connected in series, power battery (1) is connected with the front end of energy consumption adjustable resistance (2) through DC bus, the rear end of energy consumption adjustable resistance (2) is connected with the front end of motor controller (3) through DC bus, and the rear end of motor controller (3) is connected with hub motor (4) through three-phase AC bus; Small EMB control system (B) is composed of power battery (1), small EMB (6), EMB controller (7) and DC / DC converter (8), which are arranged in order from left to right and connected in series, power battery (1) is connected with the left end of DC / DC converter (8) through DC bus, the right end of DC / DC converter (8) is connected with the left end of EMB controller (7) through DC bus, and the right end of EMB controller (7) is connected with small EMB (6) through three-phase AC bus; The hub motor (4) of the hub motor control system (A) is fixedly connected to the hub of the wheel (5); The small EMB (6) of the small EMB control system (B) is fixedly connected to the hub of the wheel (5); 2) The working mode of hub motor control system (A) includes motor driving mode and motor braking mode, specifically: 2.1 Motor driving mode: power battery (1) outputs high voltage DC through DC bus, flows to motor controller (3) through energy consumption adjustable resistance (2), motor controller (3) converts two-phase DC into three-phase AC and outputs to hub motor (4) for driving torque control, hub motor (4) drives wheel (5) to rotate, at this time, in order to reduce output loss, the resistance value of energy consumption adjustable resistance (2) is adjusted to 0; 2.2 Motor braking mode: Motor braking needs negative torque current. According to the different sources of negative torque current, motor braking mode includes: Motor regenerative braking, energy consumption braking and motor power consumption braking, specifically: 2.2.1 When in motor regenerative braking, negative torque current comes from hub motor (4) and finally flows to power battery (1), at this time, the kinetic energy of rotating wheel (5) drives the rotor of hub motor (4) to rotate, according to Faraday's law of electromagnetic induction, when the rotor rotates, the stator coil will induce a counter electromotive force, motor controller (3) adjusts the working state of internal IGBT to make the electronic stator coil generate negative torque current to realize braking, and the negative torque current flows through energy consumption adjustable resistance (2) to charge power battery (1), at this time, in order to improve the energy recovery effect, energy consumption adjustable resistance (2) is adjusted to 0; 2.2.2 When in energy-consuming braking, negative torque current comes from the wheel hub motor (4) and finally flows to the energy-consuming adjustable resistor (2). At this time, the kinetic energy of the rotating wheel (5) drives the rotor of the wheel hub motor (4) to rotate. According to Faraday's law of electromagnetic induction, when the rotor rotates, an induced electromotive force will be generated in the stator coil. The motor controller (3) adjusts the working state of the internal IGBT to make the induced electromotive force generated by the motor stator coil act on the energy-consuming adjustable resistor (2), generating negative torque current to achieve braking. By adjusting the resistance value of the energy-consuming adjustable resistor (2), the kinetic energy of the wheel hub motor (4) is completely converted into heat energy dissipated by the resistor. However, at this time, although braking is achieved, the kinetic energy cannot be recovered. Energy-consuming braking and motor regenerative braking can be performed simultaneously. From the perspective of improving energy utilization, motor regenerative braking is normally used. When motor regenerative braking cannot meet the braking demand, energy-consuming braking is used to supplement. Energy-consuming braking cannot be performed simultaneously with the other two braking modes. 2.2.3 When in motor power-consuming braking, negative current comes from the power battery (1). At this time, the motor controller (3) adjusts the working state of the internal IGBT to make the motor stator generate negative current, thereby making the motor generate braking torque to achieve braking. The wheel hub motor (4) needs to consume electric energy to brake and cannot recover the braking energy. Power-consuming braking is performed when the motor speed is too low or the battery is fully charged and cannot be charged. Power-consuming braking cannot be performed simultaneously with the other two braking modes. 3) The working mode of the small EMB control system (B) is EMB friction braking: The power battery (1) outputs high-voltage direct current through the direct current bus, which is converted into low-voltage direct current by the DC / DC converter (8) and input to the EMB controller (7). The EMB controller (7) converts two-phase direct current into three-phase alternating current and outputs it to the small EMB (6) for braking torque control. 4) The braking mode judgment includes the following steps: 4.1 Determine whether the vehicle speed is less than 5 km / h. If yes, directly perform motor power-consuming braking; 4.2 Otherwise, continue to determine whether the current SOC of the power battery (1) is less than 90%. If yes, continue to determine whether the current total demand braking torque is less than the current maximum regenerative torque of the motor. If yes, perform motor regenerative braking; 4.3 Otherwise, continue to determine whether the current wheel hub motor (4) is in the constant power zone. If yes, continue to determine whether the current total demand braking torque is less than the sum of the current maximum regenerative torque of the motor and the maximum energy-consuming braking torque. If yes, perform motor regenerative braking and energy-consuming braking simultaneously. Adjust the resistance value of the energy-consuming adjustable resistor (2) to make the wheel hub motor (4) provide the maximum regenerative braking torque it can provide, and the remaining braking torque is provided by energy-consuming braking. 4.4 Otherwise, the maximum regenerative torque and the maximum energy consumption braking torque of the motor still cannot meet the braking demand. At this time, the motor regenerative braking, energy consumption braking and EMB friction braking are performed simultaneously. The hub motor (4) provides the maximum regenerative braking torque that can be provided at present, the resistance of the energy consumption adjustable resistor (2) is adjusted to the upper limit to provide the maximum energy consumption braking torque, and the remaining demand braking torque is provided by the EMB friction braking; 4.5 If the current motor is in the constant torque zone, in order to ensure the maximum energy recovery effect, the resistance of the energy consumption resistor is adjusted to 0. At this time, the motor regenerative braking and the EMB friction braking are performed. The hub motor (4) provides the maximum regenerative braking torque that can be provided at present, and the remaining demand braking torque is provided by the EMB friction braking; 4.6 If the SOC of the current power battery (1) is greater than 90%, the motor kinetic energy cannot be recovered to charge the power battery (1) at this time, that is, the motor regenerative braking cannot be performed. Continue to determine whether the current total demand braking torque is less than the maximum energy consumption braking torque. If yes, the energy consumption braking is directly performed; 4.7 Otherwise, the energy consumption braking and the EMB friction braking are performed simultaneously. The resistance of the energy consumption resistor is adjusted to the upper limit to provide the maximum energy consumption braking torque, and the remaining demand braking torque is provided by the EMB friction braking.

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