System and method for controlling a traction motor
The traction motor control system addresses abrupt regenerative braking cutoffs by generating counter torque based on SoC, slippage, temperature, and speed, ensuring consistent braking and improved safety in electric vehicles.
Patent Information
- Application Number
- JP2025544422
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-02-02
- Filing Date
- 2024-01-25
- Publication Date
- 2026-02-12
AI Technical Summary
Existing regenerative braking systems in electric or hybrid vehicles abruptly switch off when the battery's State of Charge (SoC) exceeds a threshold, leading to sudden loss of braking response and vehicle control, posing safety risks and reducing occupant trust.
A system and method for controlling a traction motor that includes a control unit to detect braking operations, state of charge, and slippage, temperature, and vehicle speed to generate counter torque, ensuring consistent braking response by switching to regenerative or counter torque based on SoC, and stopping torque when conditions are unsafe.
Ensures consistent braking feel and response, preventing wheel skid, thermal stress, and reverse wheel rotation, enhancing passenger trust and safety without additional components, thus maintaining reliable braking performance.
Smart Images
Figure 2026505182000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to the control of traction motors, and more particularly to systems and methods for controlling traction motors that provide braking torque to a vehicle. [Background technology]
[0002] As vehicle technology advances, there is an increasing focus on enhancing driver assistance and the overall driving experience. Most current electric or hybrid vehicles are equipped with regenerative braking, where energy is recovered during braking and stored back in the battery. Regenerative braking involves recovering some of the kinetic energy that would normally be converted to heat and converting it into electricity. Several conventional techniques exist for controlling regenerative braking. It is well known that when the regenerative braking contribution is set to a significant value, it results in better fuel economy, better braking control response, and better overall vehicle behavior.
[0003] However, regenerative braking, which charges the battery of an electric or hybrid vehicle, also depends on the battery's SoC (State of Charge). In existing systems, regenerative braking is configured to automatically turn off whenever the SoC reaches a threshold, such as 90% or higher, to maintain better battery life. The problem with this limitation is that this automatic switch-off of regenerative braking can occur suddenly, even during use / driving conditions, at any time when the SoC exceeds the threshold. This abrupt switch-off of regenerative braking leads to a sudden reduction in braking response to any given input to the basic braking system, thereby leading to a sudden loss of vehicle control. This leads to a significant loss of occupant trust in the braking system, thereby creating a major road safety issue. Furthermore, this loss of regenerative braking poses an additional safety risk when the vehicle is climbing a slope.
[0004] Certain existing systems for regenerative braking control address the problem of preventing battery overcharging by turning off regenerative braking through various techniques. Other existing systems focus on the contribution of regenerative braking when the battery's SoC exceeds a threshold by dumping the regenerated kinetic energy with a rheostat, preventing it from contributing any useful work. This also results in additional components and an increase in the vehicle's overall weight. However, none of the prior art addresses the problem of loss of braking response and loss of vehicle control due to switching off regenerative braking when the SoC exceeds a certain threshold. Summary of the Invention [Problem to be solved by the invention]
[0005] Therefore, there is a need in the art for a system and method for controlling a traction motor that addresses at least the above-mentioned problems. [Means for solving the problem]
[0006] In one aspect, the present invention relates to a system for controlling a traction motor. The system includes a power source, a traction motor, and a control unit. The control unit is configured to detect a braking operation and determine a state of charge of the power source. The control unit is further configured to operate the traction motor to receive torque from a vehicle wheel and provide electrical energy to the power source during a braking operation when the state of charge of the power source is less than a first predetermined value. The control unit is further configured to receive electrical energy from the power source and operate the traction motor to provide braking torque to the wheel by generating a counter torque during a braking operation when the state of charge of the power source is equal to or greater than the first predetermined value. The control unit is further configured to detect slippage of the wheel or traction motor rotor when the state of charge of the power source is equal to or greater than the first predetermined value, and to stop providing braking torque to the vehicle wheel by stopping operation of the traction motor and thereby stopping the counter torque when the detected slippage is equal to or greater than a second predetermined value.
[0007] In one embodiment of the present invention, the control unit includes a first phase high-side MOSFET and a first phase low-side MOSFET, a second phase high-side MOSFET and a second phase low-side MOSFET, and a third phase high-side MOSFET and a third phase low-side MOSFET, and is configured to, during a braking operation, when the state of charge of the power supply is greater than or equal to a first predetermined value, change the order of the second phase high-side MOSFET and the second phase low-side MOSFET and the third phase high-side MOSFET and the third phase low-side MOSFET to operate the traction motor to provide braking torque to the vehicle wheels by generating a counter torque.
[0008] In another embodiment of the invention, the control unit is configured to detect a control unit reverse current vector when the detected slip is less than a second predetermined value, detect a temperature of the control unit or traction motor when the detected control unit reverse current vector is greater than or equal to a third predetermined value, and stop providing braking torque to the vehicle wheels by stopping operating the traction motor and thereby stopping reverse torque when the detected temperature is greater than or equal to a fourth predetermined value.
[0009] In another embodiment of the invention, the control unit is configured to sense the speed of the vehicle when the sensed control unit reverse current vector is less than a third predetermined value, and to stop providing braking torque to the wheels of the vehicle by stopping operating the traction motors to stop the reverse torque when the sensed speed of the vehicle is equal to or less than a fifth predetermined value.
[0010] In another aspect, the present invention provides a method of controlling a traction motor that provides braking torque to a vehicle, the method comprising the steps of detecting a braking operation of the vehicle, determining a state of charge of a vehicle power source, operating the traction motor to receive torque from wheels of the vehicle and provide electrical energy to the vehicle's power source during the braking operation if the state of charge of the power source is less than a first predetermined value, operating the traction motor to receive electrical energy from the power source and provide braking torque to wheels of the vehicle by generating counter torque during the braking operation if the state of charge of the power source is equal to or greater than the first predetermined value, detecting wheel or traction motor rotor slip when the state of charge of the power source is equal to or greater than the first predetermined value, and a control unit ceasing to provide braking torque to wheels of the vehicle by ceasing operation of the traction motor to ceasing counter torque when the detected slip is equal to or greater than a second predetermined value.
[0011] In one embodiment of the present invention, the method includes operating the traction motor during a braking operation to provide braking torque to the vehicle wheels by changing the sequence of the second phase high-side MOSFET and the second phase low-side MOSFET and the third phase high-side MOSFET and the third phase low-side MOSFET to generate a counter torque when the state of charge of the power supply is greater than or equal to a first predetermined value.
[0012] In one embodiment of the present invention, the method includes detecting a control unit reverse current vector when the detected slip is less than a second predetermined value; detecting a temperature of the control unit or traction motor when the detected control unit reverse current vector is greater than or equal to a third predetermined value; and ceasing operation of the traction motor to ceasing the reverse torque and thereby ceasing to provide braking torque to the vehicle wheels when the detected temperature is greater than or equal to a fourth predetermined value.
[0013] In another embodiment of the invention, the method includes the steps of sensing a speed of the vehicle when the sensed control unit reverse current vector is less than a third predetermined value, and ceasing to provide braking torque to the wheels of the vehicle by ceasing to operate the traction motors to ceasing the reverse torque when the sensed speed of the vehicle is equal to or less than a fifth predetermined value.
[0014] Reference will now be made to embodiments of the present invention, examples of which may be illustrated in the accompanying drawings. These drawings are intended for purposes of illustration and not limitation. While the invention will generally be described in the context of these embodiments, it will be understood that it is not intended to limit the scope of the invention to these particular embodiments. [Brief explanation of the drawings]
[0015] [Figure 1] FIG. 1 illustrates a system for controlling a traction motor that provides braking torque to a vehicle according to an embodiment of the present invention. [Figure 2] FIG. 2 illustrates a control unit of a system for controlling a traction motor according to an embodiment of the present invention. [Figure 3] FIG. 1 illustrates a method for controlling a traction motor that provides braking torque to a vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION
[0016] The present invention relates to the control of traction motors. More particularly, the present invention relates to systems and methods for controlling traction motors that provide braking torque to a vehicle. The systems and methods of the present invention are typically used in vehicles such as two-wheel electric or hybrid vehicles, three-wheel electric or hybrid vehicles, four-wheel electric or hybrid vehicles, or other multi-wheel electric or hybrid vehicles, as appropriate.
[0017] FIG. 1 illustrates a system 100 for controlling a traction motor 120 that provides braking torque to a vehicle (not shown). As illustrated, the system 100 includes a power source 110. In one embodiment, the power source 110 comprises a battery (not shown) or a battery pack (not shown) comprised of multiple batteries. The system 100 further includes a traction motor 120 electrically connected to the power source 110 of the vehicle. The traction motor 120 is operably connected to at least one wheel 130 of the vehicle. Thus, during a traction operation, the power source 110 provides power to the traction motor 120, which in turn provides traction or torque to the at least one wheel 130 of the vehicle. During a braking operation, the traction motor 120 converts the kinetic energy of the at least one wheel 130 into electrical energy, which is provided to charge the power source 110. In one embodiment, the traction motor 120 may be operably connected to multiple wheels of the vehicle via a transmission system, or the system 100 may have multiple traction motors 120, each traction motor 120 connected to a respective wheel of the vehicle.
[0018] As further shown in FIG. 1 , system 100 includes a control unit 140. Control unit 140 is coupled to traction motor 120 and configured to control operation of traction motor 120. Control unit 140 is configured to detect vehicle braking. In that regard, in one embodiment, control unit 140 is coupled to a brake switch 150 of the vehicle. When a brake pedal or brake lever is depressed or activated, brake switch 150 is activated to illuminate the brake lights. Brake switch 150 is in communication with control unit 140, which detects activation of brake switch 150, thereby detecting vehicle braking. Control unit 140 is also configured to determine a state of charge of power source 110. Thus, control unit 140 determines whether the state of charge of power source 110 is less than, equal to, or greater than a first predetermined value.
[0019] Additionally, control unit 140 is configured to operate traction motor 120 to receive torque from vehicle wheels 130 and provide electrical energy to vehicle power source 110 when the state of charge of power source 110 is less than a first predetermined value during a braking operation. Thus, when control unit 140 determines that the state of charge of power source 110 is less than the first predetermined value during a braking operation, control unit 140 operates traction motor 120 to perform regenerative braking by receiving torque from wheels 130 and providing electrical energy to power source 110.
[0020] If, during a braking operation, the control unit 140 determines that the state of charge of the power source 110 is equal to or greater than a first predetermined value, the regenerative braking described above is not performed to prevent the power source 110 from overcharging and to preserve the lifespan of the power source 110. However, to prevent a loss of braking response or vehicle control during this condition, when the state of charge of the power source 110 is equal to or greater than the first predetermined value during a braking operation, the control unit 140 is configured to receive electrical energy from the power source 110 and operate the traction motor 120 to provide a braking torque to the vehicle wheels 130 by generating a counter torque. In this manner, the counter torque generated by the traction motor 120 has a similar effect on the braking operation as regenerative braking, thereby ensuring that the braking characteristics or resulting braking response are consistent regardless of the state of charge of the power source 110. This ensures a reliable and consistent braking operation, which leads to a better passenger experience and a safer riding condition. In one embodiment, the first predetermined value for the state of charge of the power source 110 is 90%. Thus, in operation, during a braking maneuver, if the state of charge is less than 90%, control unit 140 performs regenerative braking by operating traction motor 120 to receive torque from wheels 130 and provide electrical energy to power source 110. Conversely, during a braking maneuver, if the state of charge is 90% or greater, control unit 140 operates traction motor 120 to receive electrical energy from power source 110 and generate counter torque such that the resulting braking response and vehicle control remain the same while braking with constant effort.
[0021] However, if uncontrolled or improperly controlled, the provision or generation of counter torque by the traction motor can cause the wheels 130 to skid, thereby causing the vehicle to skid. To address this, the control unit 140 is further configured to detect slippage of the wheels 130 or the traction motor rotor when the state of charge of the power source 110 is greater than or equal to a first predetermined value. The control unit 140 determines whether the detected slip is less than, equal to, or greater than a second predetermined value. The control unit 140 is further configured to stop operating the traction motor 120 and thus stop the counter torque when the detected slip is greater than or equal to the second predetermined value. As a result, the traction motor stops providing braking torque to the vehicle wheels 130 when the detected slip is greater than or equal to the second predetermined value, thereby preventing wheel skid or vehicle skid. Conversely, if the detected slip is less than the second predetermined value, the control unit 140 continues to operate the traction 120 to provide a counter torque to provide a braking torque to the wheels of the vehicle.
[0022] In one embodiment, as shown in FIG. 2 , the control unit 140 includes a first-phase high-side metal-oxide-semiconductor field-effect transistor (MOSFET) 140A and a first-phase low-side MOSFET 140A′. The control unit 140 further includes a second-phase high-side MOSFET 140B and a second-phase low-side MOSFET 140B′. The control unit 140 further includes a third-phase high-side MOSFET 140C and a third-phase low-side MOSFET 140C′. In that regard, the high-side MOSFETs 140A, 140B, and 140C are connected to the positive terminal of the power supply 110, and the low-side MOSFETs 140A′, 140B′, and 140C′ are connected to the negative terminal of the power supply 110. Furthermore, the first-phase, second-phase, and third-phase MOSFETs are respectively connected to phase coils of the traction motor 120 to control the traction motor 120 in three phases.
[0023] Herein, during a braking operation, if the state of charge of the power supply 110 is greater than or equal to a first predetermined value, the control unit 140 is configured to reorder the second phase high-side MOSFET 140B and the second phase low-side MOSFET 140B' for generating a counter torque. The control unit 140 is also configured to reorder the third phase high-side MOSFET 140C and the third phase low-side MOSFET 140C'. This reordering thus operates the traction motor 120 to provide a braking torque to the vehicle wheels 130 by generating a counter torque.
[0024] In one embodiment, to prevent inappropriate or unnecessary use of counter torque, control unit 140 is configured to detect a control unit reverse current vector when the detected slip is less than a second predetermined value. Control unit 140 determines whether the control unit reverse current vector is less than, equal to, or greater than a third predetermined value. If the control unit reverse torque value is equal to or greater than the third predetermined value, control unit 140 is configured to determine the temperature of traction motor 120 or control unit 140 to prevent thermal stress on traction motor 120 and the MOSFETs. Control unit 140 determines whether the temperature of traction motor 120 or control unit 140 is less than, equal to, or greater than a fourth predetermined value. To prevent thermal stress, control unit 140 is configured to stop operating traction motor 120 and stop counter torque if the temperature of traction motor 120 or control unit 140 exceeds the fourth predetermined value. As a result, if the temperature of traction motor 120 or control unit 140 exceeds the fourth predetermined value, traction motor 120 is stopped from providing braking torque to vehicle wheels 130, thereby preventing thermal stress. Conversely, if the temperature of control unit 140 or traction motor 120 is at or below the fourth predetermined value, control unit 140 continues to operate traction motor 120 to provide counter torque to provide braking torque to vehicle wheels.
[0025] The counter torque generated by the traction motor 120 also depends on the vehicle speed. In particular, at lower vehicle speeds, providing counter torque may cause the vehicle wheels 130 to rotate in the opposite direction. To account for this, in one embodiment, the control unit 140 is configured to detect the vehicle speed when the control unit reverse current vector is less than a third predetermined value. Thus, the control unit 140 determines whether the vehicle speed is less than, equal to, or greater than a fifth predetermined value. If the determined vehicle speed is less than or equal to the fifth predetermined value, the control unit 140 is configured to stop operating the traction motor 120 and stop the counter torque. As a result, when the vehicle speed is less than or equal to the fifth predetermined value, the traction motor stops providing braking torque to the vehicle wheels 130, thereby preventing the wheels from rotating in the opposite direction. Conversely, if the vehicle speed is above the fifth predetermined value, the control unit 140 continues to operate the traction 120 to provide a counter torque to provide a braking torque to the wheels of the vehicle. In one embodiment, the fifth predetermined value of the vehicle speed is 1 Kmph.
[0026] In another aspect, the present invention relates to a method 200 for controlling a traction motor 120 that provides braking torque to a vehicle. Method steps included in a method 200 for controlling a traction motor 120 according to an embodiment of the present invention are illustrated in FIG. 3. As shown, in step 202, a braking operation of the vehicle is detected by the control unit 140. In step 204, the state of charge of the vehicle's power source 110 is detected by the control unit 140. The control unit 140 determines, among other things, whether the state of charge of the power source 110 is less than, equal to, or greater than a first predetermined value. If, in step 204, it is determined that the state of charge of the power source 110 is less than the first predetermined value during a braking operation, the method 200 proceeds to step 222, in which the control unit 140 operates the traction motor 120 to receive torque from the vehicle's wheels 130 and provide electrical energy to the vehicle's power source 110 for regenerative braking. Thereafter, in step 224, the control unit 140 checks again for braking, and if braking is detected, i.e., the brake switch 150 is detected to be on, the method 200 returns to step 222 and continues operation, and if braking is not detected, i.e., the brake switch 150 is detected to be off, the process is stopped in step 226 until a braking operation is detected.
[0027] If, in step 204, it is determined that the state of charge of the power source 110 is greater than or equal to the first predetermined value during a braking operation, the method 200 proceeds to step 206. In step 206, the control unit 140 receives electrical energy from the power source 110 and the traction motor 120 operates to provide braking torque to the vehicle wheels 130 by generating a counter torque. In step 206, the second phase high-side MOSFET 140B and the second phase low-side MOSFET 140B' are reordered and the third phase high-side MOSFET 140C and the third phase low-side MOSFET 140C' are reordered to operate the traction motor 120 to provide braking torque to the vehicle wheels 130 by generating a counter torque.
[0028] Thereafter, slippage of the wheel 130 or traction motor 120 rotor is detected by the control unit in step 208. If the slippage of the wheel 130 or traction motor 120 rotor is greater than or equal to a second predetermined value, method 200 proceeds to step 210, where counter torque is terminated by control unit 140 to prevent wheel skid or vehicle skid. If the slippage of the wheel 130 or traction motor 120 rotor is less than the second predetermined value, method 200 proceeds to step 212. In step 212, a control unit reverse current vector is determined by control unit 140. If the control unit reverse current vector is determined to be greater than or equal to a third predetermined value in step 212, method 200 proceeds to step 214 to prevent improper application of counter torque.
[0029] In step 214, the temperature of the traction motor 120 or control unit 140 is sensed by the control unit 140. If in step 214 the temperature of the traction motor 120 or control unit 140 is sensed to be above a fourth predetermined value, method 200 proceeds to step 216 to prevent thermal stress. In step 216, counter torque is stopped by the control unit 140 to prevent thermal stress, and the high temperature of the traction motor 120 or control unit 140 is notified to a vehicle occupant until a service reset is performed. If in step 214 the temperature of the traction motor 120 or control unit 140 is sensed to be below the fourth predetermined value, method 200 returns to step 206 and continues operation.
[0030] If, in step 212, the control unit reverse current vector is determined to be less than a third predetermined value, method 200 proceeds to step 218. In step 218, the vehicle speed is sensed by control unit 140 to prevent reverse wheel rotation due to the application of counter torque. If, in step 218, the vehicle speed is determined to be less than or equal to a fifth predetermined value, then, in step 220, the control unit 140 terminates the counter torque to prevent reverse rotation of vehicle wheels 130. If, in step 218, the vehicle speed is determined to be greater than the fifth predetermined value, method 200 returns to step 204 and continues operation.
[0031] Advantageously, the present invention provides a system and method for controlling a traction motor that provides braking torque to a vehicle such that, during a braking operation, a counter torque is generated and regenerative braking is terminated when the state of charge of the power source exceeds a first predetermined value. Because the counter torque affects braking characteristics similar to regenerative braking, there is no loss of braking response and loss of vehicle control due to regenerative braking being switched off when the SoC exceeds a certain threshold. Therefore, a passenger does not perceive any difference in braking feel or response when regenerative braking is on or off. This ensures greater passenger trust and reliability in the braking system, and therefore a safer passenger experience.
[0032] Additionally, using a control unit reverse current vector in controlling the traction motor to provide braking torque ensures that unnecessary or inappropriate use of reverse torque is eliminated. Similarly, sensing the temperature of the traction motor or control unit in controlling the traction motor to provide braking torque ensures that thermal stress on the traction motor or control unit is eliminated. Similarly, sensing the vehicle speed in controlling the traction motor to provide braking torque ensures that the application of reverse torque does not cause the wheels to rotate reversely.
[0033] Furthermore, the present invention eliminates the need for a rheostat to dump regenerative power, eliminating the need for additional components and reducing complexity and cost. The present invention does not require any additional hardware or external power source to provide counter torque to achieve the same braking effect. The present invention also ensures that there is no loss of braking action or impairment of braking characteristics or response, even when the state of charge is high and the vehicle is climbing a slope, thereby increasing vehicle safety.
[0034] The consistent braking characteristics and braking response regardless of the state of charge of the power source provided by the present invention is expected to result in a consistent level of passenger confidence in the braking system, which translates into an overall better and safer passenger experience.
[0035] Although the present invention has been described with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention as defined in the claims below. [Explanation of symbols]
[0036] 100 Traction motor control system 110 Power supply 120 Traction Motor 130 wheels 140 Control Unit 140A First Phase High-Side MOSFET 140B Second Phase High-Side MOSFET 140C Third Phase High-Side MOSFET 140A' Low-side MOSFET of the first phase 140B' Low-side MOSFET of the second phase 140C' Third Phase Low-Side MOSFET 150 brake switch
Claims
1. A system (100) for controlling a traction motor (120) that provides braking torque to a vehicle, comprising: a power source (110); the traction motor (120) electrically connected to the power source (110) of the vehicle, the traction motor (120) operably connected to at least one wheel (130) of the vehicle; A control unit (140) comprising: Detecting a braking operation of the vehicle; determining a state of charge of the power source (110); operating the traction motor (120) to receive torque from the wheels (130) of the vehicle and to provide electrical energy to the power source (110) of the vehicle when the state of charge of the power source (110) is less than a first predetermined value during the braking operation; receiving electrical energy from the power source (110) and operating the traction motor (120) to provide a braking torque to the wheels (130) of the vehicle by generating a counter torque when the state of charge of the power source (110) is equal to or greater than the first predetermined value during the braking operation; detecting slippage of the wheel (130) or the rotor of the traction motor (120) when the state of charge of the power source (110) is equal to or greater than the first predetermined value; and ceasing to provide braking torque to the wheels of the vehicle by ceasing to operate the traction motor and ceasing the counter torque when the detected slip is equal to or greater than a second predetermined value. and a control unit configured to:
2. The control unit (140) a first phase high-side MOSFET (140A) and a first phase low-side MOSFET (140A'); a second phase high-side MOSFET (140B) and a second phase low-side MOSFET (140B'); and a third phase high-side MOSFET (140C) and a third phase low-side MOSFET (140C'), and the control unit (140) operates the traction motor (120) to provide a braking torque to the wheels (130) of the vehicle by changing the order of the second phase high-side MOSFET (140B) and the second phase low-side MOSFET (140B') and the third phase high-side MOSFET (140C) and the third phase low-side MOSFET (140C') to generate the counter torque when the state of charge of the power source (110) is equal to or greater than the first predetermined value during the braking operation. The system (100) of claim 1 configured to:
3. The control unit (140) a control unit detecting a reverse current vector when the detected slip is less than the second predetermined value; detecting a temperature of the control unit (140) or the traction motor (120) when the detected control unit reverse current vector exceeds a third predetermined value; and ceasing to provide braking torque to the wheels of the vehicle by ceasing to operate the traction motor and ceasing the counter torque when the sensed temperature exceeds a fourth predetermined value. The system (100) of claim 1 configured to:
4. The control unit (140) detecting a speed of the vehicle when the detected control unit reverse current vector is less than the third predetermined value; and ceasing to provide braking torque to the wheels (130) of the vehicle by ceasing to operate the traction motor (120) and ceasing the counter torque when the detected speed of the vehicle is equal to or less than a fifth predetermined value. The system (100) of claim 3, configured to:
5. A method (200) for controlling a traction motor (120) that provides braking torque to a vehicle, comprising: a control unit (140) detecting a braking operation of the vehicle; the control unit (140) determining a state of charge of the vehicle's power source (110); the control unit (140) operating a traction motor (120) to receive torque from wheels (130) of the vehicle and provide electrical energy to the power source (110) of the vehicle when the state of charge of the power source (110) is less than a first predetermined value during the braking operation; the control unit (140) receiving electrical energy from the power source (110) and operating the traction motor (120) to provide a braking torque to the wheels (130) of the vehicle by generating a counter torque when the state of charge of the power source (110) is equal to or greater than the first predetermined value during the braking operation; the control unit (140) detecting slippage of the wheels (130) or the rotor of the traction motor (120) when the state of charge of the power source (110) is equal to or greater than the first predetermined value; the control unit (140) ceasing to provide braking torque to the wheels (130) of the vehicle by ceasing to operate the traction motor (120) and ceasing the counter torque when the detected slip is equal to or greater than a second predetermined value; A method (200) comprising:
6. and when the state of charge of the power source (110) is equal to or greater than the first predetermined value, the control unit (140) operates the traction motor (120) to provide a braking torque to the wheels (130) of the vehicle by changing the order of the second phase high-side MOSFET (140B) and the second phase low-side MOSFET (140B') and the third phase high-side MOSFET (140C) and the third phase low-side MOSFET (140C') to generate the counter torque. The method (200) of claim 6, comprising:
7. the control unit (140) detecting a control unit reverse current vector when the detected slip is less than the second predetermined value; the control unit (140) detecting a temperature of the control unit (140) or the traction motor (120) when the detected control unit reverse current vector is equal to or greater than a third predetermined value; the control unit (140) ceasing to operate the traction motor (120) and ceasing the counter torque to provide braking torque to the wheels (130) of the vehicle when the sensed temperature is equal to or greater than a fourth predetermined value; The method (200) of claim 5, comprising:
8. the control unit (140) detecting a speed of the vehicle when the detected control unit reverse current vector is less than the third predetermined value; the control unit (140) ceasing to provide braking torque to the wheels (130) of the vehicle by ceasing to operate the traction motor (120) and ceasing the counter torque when the detected speed of the vehicle is less than or equal to a fifth predetermined value; 8. The method (200) of claim 7, comprising: