An active anti-slope method for electric vehicles based on multi-phase motors

Abstract

The present invention relates to an active hill-rolling prevention method for electric vehicles based on a multi-phase motor, comprising a multi-phase motor system. When the vehicle enters the active hill-rolling prevention mode, the system first outputs a maximum stall torque to maintain the vehicle stationary, then monitors whether the vehicle speed is falling back, determines the road condition, and utilizes the multi-mode stall of the multi-phase motor system. In combination with the ASC mode, the active hill-rolling prevention method for electric vehicles can formulate adaptive strategies for different slope conditions, thereby effectively avoiding the risk of overheating of motor windings, motor controllers, power devices, etc., as well as the risk of the vehicle rolling downhill.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicles, and more particularly to an active anti-slope method for electric vehicles based on a multi-phase motor. Background Art

[0002] Rolling down a slope means that when a vehicle is parked on an inclined slope and needs to be restarted, if the brakes are released too quickly and the clutch or accelerator does not keep up, the vehicle will slide down. If there are other vehicles behind the vehicle, it will cause a traffic accident.

[0003] Among the existing anti-slope strategies, especially the active anti-slope strategies for electric vehicles, they can be divided into two categories: the first category is that when the electric vehicle enters the active anti-slope state, the entire vehicle maintains output according to the maximum stall torque of the motor system to ensure the vehicle's safe static state until the motor or motor controller is detected to be overheated, and the over-temperature protection is executed; the second category is that when the electric vehicle enters the active anti-slope state, the motor system will gradually reduce the motor output torque by linearly derating the maximum output torque of the motor or adopting similar measures such as step-by-step torque reduction and current reduction.

[0004] However, the above two strategies have the following defects. In the first strategy, because the motor system needs to maintain the maximum stall torque, the maximum effective value of the phase current is √2 times that of the non-stall state. According to the Joule formula Q=I 2 Rt shows that the motor heats up to twice as much as in the non-stalled state. The temperature of the motor windings and the motor controller's power devices rises rapidly. Due to the delay in the temperature detection sensor, overtemperature protection may not be triggered in time, resulting in a high risk of overheating damage to the motor and motor controller. The second strategy, while avoiding the overheating risk associated with maintaining high torque and high current for extended periods, does, however, derate the output torque on steeper roads. When the output torque is less than the vehicle's gravitational component in the direction of the slope, the vehicle may roll backward and be unable to return to a standstill, posing a significant safety risk. Summary of the Invention

[0005] The purpose of the present invention is to provide an active anti-slope method for electric vehicles based on a multi-phase motor, so as to solve the overheating risk or slope risk existing in the anti-slope strategy of existing battery vehicles.

[0006] The present invention adopts the following technical solutions:

[0007] An active anti-slope method for electric vehicles based on a multi-phase motor is characterized by comprising a motor system, wherein the motor system is a multi-phase motor system, and further comprising the following steps:

[0008] In step one, when the vehicle enters the active anti-slope mode, all phase windings of the motor system enter the stall mode, and the motor system maintains the maximum stall torque output, so that the vehicle remains stationary, and then enters step two.

[0009] In step 2, the motor torque of the motor system decreases linearly, and the current of the motor system decreases linearly accordingly. During the process of decreasing the motor torque, the vehicle speed is monitored to see if it is in reverse. If reverse speed occurs, proceed to step 3; if the motor torque and motor current continue to decrease linearly to zero without reverse speed occurring, proceed to step 6.

[0010] Step three: Determine if the vehicle is on a slope, and the motor system rapidly increases the motor stall torque to an output value m that is greater than the torque required to maintain the vehicle stationary, in order to restore the vehicle to a standstill; set a motor torque threshold M. If the output value m ≤ threshold M, proceed to step four; if the output value m > threshold M, proceed to step five.

[0011] In step 4, the motor system enters semi-ASC mode, that is, part of the phase winding of the motor system is in the locked-rotor mode, maintaining the locked-rotor torque output value m, and the other phase winding is in the ASC mode until the driver takes measures and the vehicle exits the active hill-slide prevention mode.

[0012] Step 5: The motor system maintains the motor torque output value m for the output time t and sets a time threshold T. When t>threshold T, the motor torque is linearly reduced and the vehicle will roll down a slope for a short time and a short distance. If the driver does not take action at this time, the motor system restores the motor torque output value m again. This cycle repeats until the driver takes action and the vehicle exits the active anti-slope mode.

[0013] Step six: If the vehicle is on a flat road, the motor system enters the full ASC mode, that is, all phase windings of the motor system enter the ASC mode until the driver takes measures and then exits the active anti-slope mode.

[0014] Furthermore, the multi-phase motor system may be a five-phase motor system, a six-phase motor system, a nine-phase motor system or a twelve-phase motor system.

[0015] Furthermore, the motor torque threshold M is the torque value that can be output by the phase winding when in the locked-rotor mode in step four.

[0016] Furthermore, in step four, the phase windings in the locked-rotor mode and the phase windings in the ASC mode are interchanged in working mode after a certain period of time, and the cycle is repeated until the driver takes measures and the vehicle exits the active anti-slope mode.

[0017] Furthermore, the threshold value T is the maximum operating time during which the motor winding and the motor controller do not experience overheating protection when the motor torque output value is m.

[0018] Furthermore, when the multi-phase motor system is a six-phase motor system, the six-phase motor system includes an L1 phase winding, an L2 phase winding, an L3 phase winding, an L4 phase winding, an L5 phase winding and an L6 phase winding. In step 4, the L1 phase winding, the L3 phase winding and the L5 phase winding are in a locked-rotor mode, and the L2 phase winding, the L4 phase winding and the L6 phase winding are in an ASC mode.

[0019] From the above description of the structure of the present invention, it can be seen that compared with the prior art, the present invention has the following advantages:

[0020] 1. When the vehicle of the present invention enters the active anti-slope mode, the multi-phase motor system first outputs the maximum stall torque to maintain the vehicle stationary, and then monitors whether the vehicle speed is reversed to determine the road condition. The multi-mode stall of the multi-phase motor system is used in combination with the active anti-slope method for electric vehicles formulated in the ASC mode. Adaptive strategies can be made for different slope conditions, thereby effectively avoiding the risk of overheating of the motor windings, motor controller, power device, etc. and the risk of the vehicle rolling down the slope.

[0021] 2. When driving on flat roads, the present invention reduces the motor torque output and current output to zero, and all phase windings enter the ASC mode, eliminating the risk of slope slippage and greatly reducing heat accumulation.

[0022] 3. Under working conditions with a small slope or light vehicle weight, the present invention adopts a semi-ASC mode, that is, the phase winding of the motor system is divided into two parts, one part is in the locked-rotor mode, and the other part is in the ASC mode, and these two parts of the phase winding alternately work in an alternating mode, so that the phase winding of the motor system can be cooled alternately, thereby extending the effective locked-rotor time.

[0023] 4. Under working conditions with a large slope or a heavy vehicle weight, the present invention adopts a method of dividing the sliding slope time and sliding slope distance. That is, when the motor system maintains the stall torque output value m, the maximum working time threshold T of the motor is set. When the actual output maintenance time t is greater than the set threshold T, the motor torque decreases linearly, causing the vehicle to slide down the slope for a short time and a short distance. Then, if the driver does not take any measures, the braking is continued to restore the motor stall torque output value m. This process is repeated, and the entire sliding slope process is divided into several short sliding slopes of short time and short distance, thereby minimizing the risk of overheating and sliding slope. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the full ASC mode of the six-phase motor phase winding of the present invention.

[0025] Figure 2 Schematic diagram of the semi-ASC mode of the phase winding of the six-phase motor of the present invention.

[0026] Figure 3This is a logic diagram of the active anti-slope method of the present invention. DETAILED DESCRIPTION

[0027] The specific implementation of the embodiment of the present invention is described below with reference to the accompanying drawings.

[0028] Reference Figures 1 to 3 An active slope prevention method for electric vehicles based on a multi-phase motor includes a motor system. The motor system is a multi-phase motor system, which can be a five-phase motor system, a six-phase motor system, a nine-phase motor system, or a twelve-phase motor system. In this embodiment, a six-phase motor system is used as an example. The six-phase motor system includes an L1 phase winding, an L2 phase winding, an L3 phase winding, an L4 phase winding, an L5 phase winding, and an L6 phase winding. The active slope prevention method includes the following steps:

[0029] Step 1: When the vehicle enters the active anti-slope mode, forced braking is performed, that is, all phase windings of the motor system enter the stall mode, and the motor system maintains the maximum stall torque output, so that the vehicle remains stationary, and then enters step 2.

[0030] Step 2: Determine the road condition. The motor torque of the motor system decreases linearly, and the current of the motor system decreases linearly accordingly. During the decrease of the motor torque, monitor whether the vehicle speed reverses. If reverse speed occurs, proceed to step 3; if the motor torque and motor current maintain a linear decrease to zero and no reverse speed occurs, proceed to step 6.

[0031] Step three: Determine if the vehicle is on a slope, and the motor system rapidly increases the motor stall torque to an output value m that is greater than the torque required to maintain the vehicle stationary, in order to restore the vehicle to a standstill; set a motor torque threshold M. If the output value m ≤ threshold M, proceed to step four; if the output value m > threshold M, proceed to step five.

[0032] In step 4, the motor system enters semi-ASC mode, that is, one phase winding of the motor system is in stall mode, maintaining the stall torque output value m, and the other phase winding is in ASC mode. The working modes of the two phase windings are interchanged after a certain period of time, and the cycle is repeated until the driver takes measures and the vehicle exits the active hill-slide prevention mode.

[0033] In this embodiment, the L1, L3, and L5 phase windings are in locked-rotor mode, while the L2, L4, and L6 phase windings are in active short-circuit (ASC) mode. The operating modes of the L1, L3, and L5 phase windings are swapped with those of the L2, L4, and L6 phase windings at regular intervals, thereby preventing some phase windings from operating in a locked-rotor mode and triggering overheating protection. This cyclical, alternating operating mode allows the motor system's phase windings to alternately cool, extending the effective locked-rotor time. In this embodiment, threshold M represents the maximum torque output value that can be output by the motor system's L1, L3, and L5 phase windings or the L2, L4, and L6 phase windings in locked-rotor mode. This value can be calibrated based on the motor model. ASC mode is the operating state of the motor system in active short-circuit mode.

[0034] In step five, the motor system maintains the motor torque output value m for a time t. A time threshold T is set. When t > threshold T, the motor torque is linearly reduced, causing the vehicle to roll down a short, short slope. If the driver does not take action at this point, the motor system restores the motor torque output value m. This cycle repeats until the driver takes action, at which point the vehicle exits active hill-roll prevention mode. Threshold T is the maximum operating time for the motor windings and motor controller to operate without triggering overheating protection when the motor torque output value is m. Threshold T can be calculated based on the six-phase motor model parameters to determine the maximum operating time for triggering overheating protection. This is then calibrated using the motor torque and current equation to determine the maximum operating time for the motor windings and motor controller to operate without triggering overheating protection when the motor torque output value is m. During this process, the motor system does not maintain maximum torque continuously, resulting in a minimal cumulative temperature rise. Ultimately, the motor winding temperature and the motor controller power device temperature remain stable, well below the thermal limit threshold, preventing damage to the power devices and effectively mitigating the risks of overheating and hill-rolling.

[0035] Step 6: After determining that the vehicle is on a flat surface, the motor system enters full ASC mode, effectively switching all phase windings to ASC mode until the driver takes action, at which point the active hill-roll prevention mode exits. During this process, the motor phase windings, motor controller, and power devices generate minimal heat and operate for a short period of time. The accumulated heat is far below the thermal limit, preventing damage to the power devices and effectively mitigating the risks of overheating and hill-rolling.

[0036] In the above steps, the measures taken by the driver are any one of pressing the accelerator, pressing the brake pedal or pulling the handbrake.

[0037] The present invention fully utilizes the multi-mode stalling of the multi-phase motor system and combines it with the ASC mode to develop an active anti-slope rolling method for electric vehicles. It can make adaptive strategies for different slope conditions, thereby effectively avoiding the overheating risks of motor windings, motor controllers, power devices, etc. and the risk of vehicle rolling.

[0038] More specifically, the present invention adopts steps 2 and 6 to reduce the motor torque output and current output to zero when driving on a flat road. The motor phase winding is in ASC mode, eliminating the risk of slope slippage and greatly reducing heat accumulation.

[0039] Under conditions where the slope is small or the vehicle weight is light, steps three and four are adopted, that is, the phase winding of the motor system is divided into two parts, one part is in the stall mode and the other part is in the ASC mode, and these two parts of the phase winding alternately work in an alternating working mode, so that the phase winding of the motor system can be cooled alternately, thereby extending the effective stall time.

[0040] Under conditions where the slope is large or the vehicle is heavy, steps three and five are adopted. That is, when the motor system maintains the stall torque output value m, the maximum motor operating time threshold T is set. When the actual output maintenance time t is greater than the set threshold T, the motor torque is linearly reduced, causing the vehicle to roll down the slope for a short time and a short distance. Then, if the driver does not take any measures, braking is continued to restore the motor stall torque output value m. This process is repeated, dividing the entire rolling process into several short rolling segments of short time and short distance, thereby minimizing the risk of overheating and rolling.

[0041] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. An active anti-slope method for electric vehicles based on a multi-phase motor, characterized by: The method comprises a motor system, wherein the motor system is a multi-phase motor system, and further comprises the following steps: Step 1: When the vehicle enters the active hill-slide prevention mode, all phase windings of the motor system enter the locked-rotor mode, and the motor system maintains the maximum locked-rotor torque output to keep the vehicle stationary, and then enters step 2; In step 2, the motor torque of the motor system decreases linearly, and the current of the motor system decreases linearly accordingly. During the process of the motor torque decreasing, the vehicle speed is monitored to see if reverse speed occurs. If reverse speed occurs, the process proceeds to step 3. If the motor torque and motor current continue to decrease linearly to zero without reverse speed occurring, the process proceeds to step 6. Step 3: Determine if the vehicle is on a slope. The motor system rapidly increases the motor stall torque to an output value m greater than the torque required to maintain the vehicle stationary, in order to restore the vehicle to a standstill. Set a motor torque threshold M. If the output value m ≤ the threshold M, proceed to step 4. If the output value m > the threshold M, proceed to step 5. Step 4: The motor system enters semi-ASC mode, that is, one phase winding of the motor system is in locked-rotor mode, maintaining the locked-rotor torque output value m, while the other phase winding is in ASC mode until the driver takes action and the vehicle exits active hill-slide prevention mode; Step 5: The motor system maintains the motor torque output value m for a time t. A time threshold T is set. When t>threshold T, the motor torque is linearly reduced, causing the vehicle to roll down a short slope for a short period of time. If the driver does not take action at this time, the motor system restores the motor torque output value m. This cycle repeats until the driver takes action, at which point the vehicle exits the active hill-rolling prevention mode. Step six: If the vehicle is on a flat road, the motor system enters the full ASC mode, that is, all phase windings of the motor system enter the ASC mode until the driver takes measures and then exits the active anti-slope mode.

2. The active anti-slope method for electric vehicles based on a multi-phase motor according to claim 1, characterized in that: The multi-phase motor system is a five-phase motor system, a six-phase motor system, a nine-phase motor system or a twelve-phase motor system.

3. The active anti-slope method for electric vehicles based on a multi-phase motor according to claim 1, characterized in that: The motor torque threshold M is the torque value that can be output by the phase winding when in the locked-rotor mode in step 4.

4. The active anti-slope method for electric vehicles based on a multi-phase motor according to claim 1, characterized in that: In the fourth step, the phase windings in the locked-rotor mode and the phase windings in the ASC mode are interchanged in working mode after a certain period of time, and the cycle is repeated until the driver takes measures and the vehicle exits the active anti-slope mode.

5. The active anti-slope method for electric vehicles based on a multi-phase motor according to claim 1, characterized in that: The threshold value T is the maximum working time of the motor winding and the motor controller without overheating protection when the motor torque output value is m.

6. The active anti-slope method for electric vehicles based on a multi-phase motor according to claim 2, characterized in that: When the multi-phase motor system is a six-phase motor system, the six-phase motor system includes an L1 phase winding, an L2 phase winding, an L3 phase winding, an L4 phase winding, an L5 phase winding and an L6 phase winding. In step 4, the L1 phase winding, the L3 phase winding and the L5 phase winding are in a locked-rotor mode, and the L2 phase winding, the L4 phase winding and the L6 phase winding are in an ASC mode.

7. The active anti-slope method for electric vehicles based on a multi-phase motor according to claim 1, characterized in that: The driver takes action by stepping on the accelerator, braking the brake pedal or applying the parking brake.

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