CN110873180A

CN110873180A - Synchronous gear shifting and speed changing method for two-gear gearbox of hub motor

Info

Publication number: CN110873180A
Application number: CN201911153696.0A
Authority: CN
Inventors: 王军年; 高守林; 强越
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2019-11-22
Filing date: 2019-11-22
Publication date: 2020-03-10
Anticipated expiration: 2039-11-22
Also published as: CN110873180B

Abstract

The invention discloses a synchronous gear shifting and speed changing method for a two-gear gearbox of a hub motor, which comprises the following steps of: reading system preset parameters and acquiring current vehicle running state information; step two, judging basic conditions of gear shifting according to the driving state of the automobile and the working condition of the road surface; judging the gear shifting working condition of the vehicle, and determining the gear shifting target speed; step four, determining the gear shifting target rotating speed of the hub motor; step five, judging a gear shifting condition according to the speed difference between the gear shifting target rotating speed and the actual rotating speed of the hub motor; step six, the transmission controller TCU controls the gear shifting mechanism to complete gear shifting; and seventhly, judging a gear shifting result according to the speed difference between the reference rotating speed and the actual rotating speed of the hub motor after gear shifting. According to the control method provided by the invention, on the premise of ensuring the safety, the synchronous gear shifting of the two-gear gearbox of the automobile hub motor is realized, so that the automobile can normally run according to the instruction of a driver, and the requirements of the dynamic property and the economical efficiency of the automobile are met.

Description

Synchronous gear shifting and speed changing method for two-gear gearbox of hub motor

Technical Field

The invention belongs to the field of electric automobiles, and relates to a gear shifting and speed changing control method of an electric automobile gearbox, in particular to a synchronous gear shifting and speed changing method of a distributed driving electric automobile carrying a hub motor two-gear gearbox.

Background

The rapid development of the automobile industry changes the travel mode of people and improves the life quality of people. When bringing convenience to daily life of people, a plurality of problems are brought to the people: the large consumption of non-renewable energy sources such as petroleum, natural gas and the like brings challenges to global energy supply; a large amount of tail gas is discharged, so that urban pollution, global warming and other environmental hazards are caused; the production and life of people are also seriously influenced by a large amount of noise generated by the automobile. New energy automobiles represented by electric automobiles have the advantages of low noise, zero pollution, high energy conversion rate and the like, and are increasingly paid attention to by people. With the rapid development of battery technology and charging technology, the market application of electric vehicles is guaranteed, and therefore, the electric vehicles with zero pollution and zero emission are the future trends of vehicle development.

The motor is a core component for generating power by the electric automobile, and the electric automobile is divided into a centralized driving mode and an electric wheel distributed driving mode according to different motor distribution positions. The output power of the centralized driving motor needs to be transmitted to wheels through transmission devices such as a speed changer, a speed reducer and a differential mechanism, the transmission devices increase the cost and the quality of the whole vehicle, the structure is complex, and the transmission efficiency is low. The distributed driving can directly install the motor on the driving wheel or near the wheel edge, has compact structure, small occupied space and high transmission efficiency, can reduce the quality of the whole automobile, and is one of the development trends of future electric automobiles. In-wheel motor drives are one of the main forms of distributed drives. The wheel hub motor generally divide into external rotor motor direct drive wheel form to and traditional internal rotor motor is joined in marriage reduction gear drive wheel form, but whatever kind of mode, adopt and directly drive or single velocity ratio drive all can be because of the complexity of car operating mode, or lead to operating mode dynamic such as climbing not enough, or the problem that economic nature is not good when driving at the uniform velocity. Therefore, the hub motor with the two-gear gearbox can reasonably switch high and low speed ratios according to the actual running working condition of the electric automobile, and meets the requirements of the dynamic property and the economical efficiency of the electric automobile.

A large amount of researches are carried out on related scholars at home and abroad of the two-gear gearbox of the hub motor. An inner rotor hub motor two-gear speed changing box with an electromagnetic brake and a one-way clutch disclosed in the earlier patent of 'a power-interruption-free inner rotor hub motor two-gear speed changing system and an electric automobile' (patent number CN110071597A) realizes power-interruption-free gear shifting of the inner rotor hub motor two-gear speed changing box by separation and locking of the electromagnetic brake; the patent "a two keep off speed change system of outer rotor in-wheel motor based on two electromagnetic brake and electric automobile" (patent number CN110126609A) discloses an outer rotor in-wheel motor two keep off speed change system with two electromagnetic brake, through the combination of two electromagnetic brake separation and locking, realizes the fender position transform of outer rotor in-wheel motor two keep off speed change system. Two patents provide two kinds of neotype in-wheel motor two-gear speed change system schemes, but do not provide the scheme to the method of controlling the synchronous variable speed of wheel in-wheel motor two-gear gearbox. At present, domestic and foreign researches are all focused on the gear shifting rule of a single-assembly two-gear gearbox in a driving scheme of a centralized arrangement single-motor two-gear gearbox, and the problem of mutual synchronization of gear shifting of the left and right wheel distributed hub motor two-gear gearboxes is rarely considered. If the distributed driving electric automobile carrying the hub motor two-gear gearbox is asynchronous in gear shifting of the left gearbox and the right gearbox, the driving force and the rotating speed of the left wheel and the right wheel are different, a yaw moment is generated, the automobile deviates from an expected driving route, and the driving safety of the automobile is seriously influenced.

Disclosure of Invention

The invention provides a synchronous gear shifting and speed changing method for a hub motor two-gear gearbox, and mainly aims to realize synchronous gear shifting and speed changing of the hub motor two-gear gearbox of a left wheel and a right wheel according to the current vehicle running state and road surface working condition and by fully considering the vehicle running safety and the intention of a driver in the running process of an automobile.

The invention provides a synchronous gear shifting and speed changing method for a two-gear gearbox of a hub motor, and also aims to try safe gear shifting again through related control strategies according to gear shifting working conditions after synchronous gear shifting of the two-gear gearbox of the hub motor of a left wheel and a right wheel fails. If the gear shifting fails again, in order to ensure that the automobile can continue to run, the gearbox is controlled to recover to the gear before the gear shifting, the running stability is ensured, and an alarm signal is sent out to remind a driver of safe driving.

The technical scheme provided by the invention is as follows:

the synchronous gear shifting and speed changing method of the two-gear gearbox of the hub motor comprises the following steps:

step one, reading transmission ratio i of each gear of a gearbox stored in a processor chip in real time by a VCU of a vehicle control unit_kSteering wheel angle threshold δ_tLongitudinal slope angle threshold α_tTransverse slope angle threshold gamma_tShift execution time threshold T_tBrake pedal opening degree threshold BP_tBefore-shift speed error threshold epsilon₁Speed error threshold epsilon after gear shifting₂A wheel radius R; the VCU of the vehicle controller acquires the current speed u of the vehicle, the gear state k of a left gearbox and a right gearbox, the steering wheel angle delta, the accelerator pedal opening AP, the brake pedal opening BP and the rotating speed n of a hub motor of a left wheel in real time through a sensor_lRight wheel hub motor speed n_rA longitudinal road slope α and a transverse road slope γ;

step two, the VCU of the vehicle controller judges basic conditions of gear shifting according to the current automobile state and road surface working conditions;

step three, the VCU of the vehicle control unit judges the gear shifting working condition of the current vehicle according to the accelerator pedal opening AP and the brake pedal opening BP, and determines the gear shifting target speed u_t；

Step four, the VCU of the vehicle control unit according to the target speed u of shifting gears_tThe gear ratio i of the current gearbox_kDetermining the target speed n of the hub motor_t；

Step five, the VCU of the vehicle control unit judges the gear shifting condition according to the speed difference between the gear shifting target rotating speed and the actual rotating speed of the hub motors of the left wheel and the right wheel;

step six, the transmission case controller TCU sends an action command to the gear shifting actuating mechanisms of the two-gear transmission case of the hub motors of the left wheel and the right wheel at the same time to complete gear shifting operation;

and seventhly, the VCU of the vehicle control unit judges a gear shifting result according to the speed difference between the reference rotating speed and the actual rotating speed of the hub motors of the left wheel and the right wheel after gear shifting, and performs corresponding operation according to the gear shifting result.

Preferably, in the second step, the basic condition of the vehicle control unit VCU for determining gear shifting according to the current vehicle state and the road surface condition is as follows:

if delta is less than or equal to delta_t，α≤α_t，γ≤γ_tThe current vehicle and road surface driving state are considered to be good, the gear shifting condition is met, otherwise, the current working condition is considered to be severe, safe gear shifting is not facilitated, the VCU of the whole vehicle controller enters a gear shifting protection state, a gear shifting instruction is not sent, and the gearbox maintains the existing gear.

Wherein, delta is the current steering wheel angle of the automobile, delta_tIs steering wheel angle threshold, α is current road surface longitudinal gradient angle, α_tIs a longitudinal slope angle threshold value, gamma is the current road surface transverse slope angle, gamma_tIs a lateral slope angle threshold.

Preferably, in the third step, the condition that the vehicle control unit VCU judges the vehicle shift condition is as follows:

and if the AP is more than 0 and the BP is 0, the automobile is considered to be in an accelerating forward state, the driver has the intention of increasing the speed of the automobile and enters an upshift working condition, otherwise, the automobile is considered to be in a sliding or braking state, the driver has the intention of reducing the speed of the automobile and enters a downshift working condition.

Wherein AP is the opening degree of an accelerator pedal, and BP is the opening degree of a brake pedal.

Preferably, in the third step, the method for determining the target gear shifting speed is divided into the following two types according to different driving conditions of the vehicle:

(1) and under the upshifting working condition, determining according to the curve of the opening degree of the accelerator pedal and the upshifting target vehicle speed.

Along with the increase of the opening degree of an accelerator pedal, the automobile needs to have stronger acceleration performance, the low-speed gear 1 has the effects of reducing and increasing torque, and the acceleration performance is better, so that the gear-shifting target speed u during gear-shifting is increased_tWith increasing opening degree of accelerator pedalAnd additionally, the method has an ascending trend, a specific gear shifting target speed value needs to be determined by comprehensively considering the dynamic property and the comfort of the automobile and adopting a real-vehicle calibration mode.

(2) And under the downshift working condition, determining according to the curve of the opening of the brake pedal and the downshift target vehicle speed.

With the increase of the opening BP of the brake pedal, a driver has the intention of quickly decelerating the automobile, and if the downshift target speed is increased, the automobile can enter a low-speed gear as soon as possible to realize quick deceleration. Thus the shift target vehicle speed u at downshift_tWith the increase of the opening degree of the brake pedal, the gear shifting target speed value has an ascending trend, the braking performance and the whole vehicle comfort are required to be comprehensively considered, and the gear shifting target speed value is determined in a real vehicle calibration mode.

If the brake pedal opening BP is larger than or equal to the set brake pedal opening threshold BP_tAnd at the moment, the vehicle is in an emergency braking state, the VCU of the vehicle controller enters a gear shifting protection state, a gear shifting instruction is not sent, and the gearbox maintains the existing gear.

Preferably, in the fourth step, the hub motor shift target speed n_tComprises the following steps:

in the formula u_tTo shift target vehicle speed, i_kThe transmission ratio of the gearbox in the k gear is shown, and R is the radius of a wheel.

Preferably, in the fifth step, the conditions for the VCU to perform the shift determination according to the speed difference between the target rotation speed and the actual rotation speed of the hub motor of the left and right wheels are as follows:

if | n_t-n_l|≤ε₁，|n_t-n_r|≤ε₁And the current difference of the rotating speeds of hub motors of the left wheel and the right wheel of the automobile is small, the slip rates of the left wheel and the right wheel are within an allowable range, the gear shifting condition is met, and the VCU of the whole automobile controller sends a gear shifting instruction to the TCU of the transmission case controller. Otherwise, the current driving state of the automobile is not favorable for safe gear shifting, the VCU of the vehicle controller enters a gear shifting protection state, no gear shifting instruction is sent, and the gearbox is maintainedThe existing gear.

Wherein n is_tFor shifting target speed, n, of the in-wheel motor_lIs the actual rotating speed of the hub motor of the left wheel, n_rIs the actual rotating speed of the hub motor of the right wheel₁Is a pre-shift speed error threshold.

Preferably, in the seventh step, the vehicle control unit VCU determines, according to a speed difference between the reference rotation speed and the actual rotation speed of the in-wheel motor after the left and right wheels are shifted, that the shift result is in a condition that:

if T is less than or equal to T_t，|n_t’-n_l|≤ε₂，|n_t’-n_r|≤ε₂And simultaneously, if the current two-gear gearbox of the hub motor of the left wheel and the right wheel is successfully shifted, the VCU of the vehicle control unit performs the reset operation of the shifting state. Otherwise, the gear shifting is failed, and the VCU sends a related instruction to perform gear shifting again according to the difference between the gear-up working condition and the gear-down working condition.

Wherein T is the shift time, T_tTo shift time threshold, n_lIs the actual rotating speed of the hub motor of the left wheel, n_rFor the actual rotation speed of the hub motor of the right wheel, n_t' reference speed of motor, epsilon corresponding to actual speed of new gear₂Is a post-shift speed error threshold.

Preferably, the new gear hub motor reference rotating speed n_t' is:

wherein u is the vehicle speed after the gear shift is finished, i_kThe' is a new gear transmission ratio after the gearbox is shifted, and R is the radius of the automobile.

Preferably, the step of performing the re-shift when the vehicle fails to shift under the upshift condition is as follows:

step one, the VCU sends a torque clearing instruction to the hub motor controller to enable the output torque of the hub motors of the left wheel and the right wheel to be zero.

And step two, the VCU of the vehicle control unit sends a two-gear exit instruction to the TCU of the gearbox controller, so that the two-gear gearbox of the left wheel and the right wheel is in a neutral gear state.

And step three, the VCU sends a two-gear-hanging instruction to the TCU, and the TCU controls the gear-shifting executing mechanism of the two-gear gearbox of the left wheel and the right wheel to act.

And step four, the VCU of the vehicle control unit sends a torque demand instruction to the hub motor controller again to enable the hub motors of the left wheel and the right wheel to recover torque output again.

Step five, the VCU of the vehicle control unit judges a gear shifting result according to the speed difference between the target rotating speed and the actual rotating speed of the hub motors of the left wheel and the right wheel after gear shifting:

if T is less than or equal to T_t，|n_t’-n_l|≤ε₂，|n_t’-n_r|≤ε₂And simultaneously, if the current two-gear gearbox of the hub motor of the left wheel and the right wheel is successfully shifted, the VCU of the vehicle control unit performs the reset operation of the shifting state. Otherwise, if the two-gear gearbox fails to upshift continuously for two times, the gearbox can be considered to have an upshift fault, the gearbox restores the first-gear state again in order to maintain the power output of the automobile, and the vehicle control unit VCU sends an upshift failure alarm to the instrument panel to prompt a driver to drive cautiously and reasonably according to the current fault information of the automobile.

Wherein T is the shift time, T_tTo shift time threshold, n_lIs the actual rotating speed of the hub motor of the left wheel, n_rFor the actual rotation speed of the hub motor of the right wheel, n_t' reference rotation speed, epsilon, for new gear hub motor₂Is a post-shift speed error threshold.

Preferably, the step of performing the re-shift when the vehicle fails to shift under the downshift condition is as follows:

step one, the VCU of the vehicle control unit sends a first gear quitting instruction to the TCU of the gearbox controller, so that the two-gear gearbox of the left wheel and the right wheel is in a neutral gear state.

And step two, the VCU sends a first gear engaging command to the TCU, and the TCU controls the gear shifting actuating mechanism of the left and right wheel two-gear gearbox to act.

Step three, the VCU of the vehicle control unit judges a gear shifting result according to the speed difference between the target rotating speed and the actual rotating speed of the hub motors of the left wheel and the right wheel after gear shifting:

if T is less than or equal to T_t，|n_t’-n_l|≤ε₂，|n_t’-n_r|≤ε₂And simultaneously, if the current two-gear gearbox of the hub motor of the left wheel and the right wheel is successfully shifted, the VCU of the vehicle control unit performs the reset operation of the shifting state. Otherwise, the two-gear gearbox fails to downshift for two times continuously, the gearbox can be considered to have a downshift fault, the gearbox restores the two-gear state again in order to maintain the normal running function of the automobile, and the vehicle control unit VCU sends a downshift failure alarm to the instrument panel to prompt a driver to drive cautiously and reasonably according to the current fault information of the automobile.

Compared with the prior art, the invention has the following beneficial effects:

1. the synchronous gear shifting and speed changing method of the hub motor two-gear gearbox fully considers the driving condition of the automobile, the road surface state and the operation intention of a driver, and realizes the synchronous gear shifting and speed changing of the hub motor two-gear gearbox of the left wheel and the right wheel on the premise of ensuring the safety.

2. The synchronous gear shifting and speed changing method of the two-gear gearbox of the hub motor is not only suitable for the hub motor system adopting the planetary gear type two-gear speed changer, but also suitable for the hub motor system adopting the parallel shaft type two-gear speed changer, and has good universality.

3. The synchronous gear shifting and speed changing method of the two-gear gearbox of the hub motor can try to shift gears to the maximum extent on the premise of ensuring the safety of an automobile, and reduces the accidental gear shifting failure probability. After the gear shifting fails, the original gear of the gearbox can be recovered, the normal running function of the automobile is continuously kept, the running stability is ensured, fault alarm information can be sent out, and a driver is reminded of driving carefully.

Drawings

Fig. 1 is a schematic diagram of a distributed independent drive electric vehicle to which the synchronous gear shifting and speed changing method of the two-gear gearbox of the hub motor is applied.

Fig. 2 is a schematic diagram of a structure of a left rear wheel assembly of an embodiment of a two-gear transmission of a hub motor, which is applicable to the synchronous gear shifting and speed changing method of the two-gear transmission of the hub motor.

Fig. 3 is a schematic diagram of a structure of a right rear wheel assembly of an embodiment of a two-gear transmission of a hub motor, which is applicable to the synchronous gear shifting and speed changing method of the two-gear transmission of the hub motor.

FIG. 4 is a main control flow chart of the synchronous shifting method of the hub motor two-gear transmission according to the present invention.

FIG. 5 is a sub-control flow chart of the gear-up working condition of the synchronous gear-shifting and speed-changing method of the two-gear gearbox of the hub motor according to the invention.

FIG. 6 is a curve of a corresponding relationship between an accelerator pedal opening and a target gear shifting vehicle speed in the synchronous gear shifting and speed changing method of the two-gear gearbox of the hub motor.

FIG. 7 is a sub-control flow chart of the downshift condition of the synchronous shifting and speed changing method of the two-gear gearbox of the hub motor according to the invention.

Fig. 8 is a curve of the correspondence between the opening degree of a brake pedal and a target vehicle speed for shifting according to the synchronous shifting and speed changing method for the two-gear gearbox of the hub motor.

Detailed Description

The present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.

As shown in fig. 1, the distributed drive electric vehicle component parts to which the in-wheel motor two-gear transmission synchronous gear shifting and speed changing method of the present invention is applied include a left rear wheel 100, a left rear wheel two-gear transmission 200, a left rear wheel in-wheel motor 300, a right rear wheel in-wheel motor 400, a right rear wheel two-gear transmission 500, a right rear wheel 600, a left rear wheel in-wheel motor controller MCU700, a power battery 800, a right rear wheel in-wheel motor controller MCU900, a power battery management system BMS1000, a vehicle controller VCU1100, and a two-gear transmission controller TCU 1200.

The right side shell of the left rear wheel two-gear transmission 200 is connected with the left side shell of the left rear wheel hub motor 300 through a bolt, and the left side shell is supported on an output shaft through a bearing. The left casing of the right rear wheel two-gear gearbox 500 is connected with the right casing of the right rear wheel hub motor 400 through bolts, and the right casing is supported on an output shaft through a bearing. The vehicle control unit VCU1100 is connected with the transmission controller TCU1200, the battery management system BMS1000, the left rear wheel hub motor controller MCU700 and the right rear wheel hub motor controller MCU900 through CAN lines.

The battery management system BMS1000 may control a charge and discharge process of the power battery 800. The left rear wheel hub motor controller MCU700 controls the output current of the power battery 600 through an internal algorithm to control the rotation speed and torque of the left rear wheel hub motor 300. The right rear wheel hub motor controller MCU900 controls the output current of the power battery 600 through an internal algorithm to control the rotation speed and torque of the right rear wheel hub motor 400. The two-gear transmission controller TCU1200 controls the shift actuators of the left and right rear wheel two-

gear transmissions

200 and 500 to change the gears of the transmission. The vehicle control unit VCU1100 sends a gear shifting instruction to the two-gear transmission case controller TCU1200 through the CAN line according to the driver instruction and the judgment on the running state information, and the two-gear transmission case controller TCU1200 CAN respond to the gear shifting instruction of the vehicle control unit VCU1100 and feed back information such as the gear position of the transmission, the state of a gear shifting execution mechanism and the like to the vehicle control unit VCU1100 through the CAN line. The vehicle control unit VCU1100 sends a demand torque or demand rotating speed instruction to the left rear wheel hub motor controller MCU700 and the right rear wheel hub motor controller MCU900 through CAN lines according to a driver instruction, the left rear wheel hub motor controller MCU700 and the right rear wheel hub motor controller MCU900 respond to the instruction of the vehicle control unit VCU1100, and the state information of the torque, the rotating speed and the like of the hub motors controlled by the left rear wheel hub motor controller MCU700 and the right rear wheel hub motor controller MCU900 is fed back to the vehicle control unit VCU1100 through the CAN lines. The vehicle control unit VCU1100 sends instructions such as charging and discharging limit power to the battery management system BMS1000 through the CAN line, and the battery management system BMS1000 responds to the instructions of the vehicle control unit VCU1100 and feeds battery state information such as current battery temperature, charging and discharging power and the like back to the vehicle control unit VCU 1100. The vehicle control unit VCU1100 acquires signals related to synchronous shifting, such as a steering wheel angle signal, a brake pedal signal, an accelerator pedal signal, a longitudinal gradient angle signal, a transverse gradient angle signal and the like acquired by a related sensor in real time through a signal terminal.

As shown in fig. 2, the left and rear wheel assembly applied to the embodiment of the hub motor two-gear transmission of the present invention mainly comprises an inner rotor hub motor 300 and a double row planetary gear type two-gear transmission 200. The first planet row sun gear 221 of the two-gear transmission case 200 is in splined connection with the rotor output shaft 301 of the inner rotor hub motor 300, and the second planet row planet carrier 232 of the two-row planet gear type two-gear transmission case 200 is in splined connection with the rim of the left rear wheel 100.

The double-row planetary gear type two-gear transmission 200 mainly comprises a No. 1 electromagnetic brake 210, a one-way clutch 211, a first planet row sun gear 221, a first planet row planet gear 222, a first planet row gear ring 223, a first planet row planet carrier 224, a No. 2 electromagnetic brake 225, a second planet row sun gear 231, a second planet row planet carrier 232, a second planet row gear ring 233 and a second planet row planet gear 234. The four working states of forward first gear, forward second gear, reverse gear and neutral gear are mainly provided.

A forward first gear state: electromagnetic brake No. 1 210 is not energized, and electromagnetic brake No. 2 225 is energized, at which time the first planetary gear set 223 is locked. The power output by the rotor hub motor 300 in the left rear wheel in the forward direction is transmitted to the left rear wheel 100 through the rotor output shaft 301, the first planet row sun gear 221, the first planet row planet carrier 224, the second planet row sun gear 231 and the second planet row planet carrier 232 in sequence. At the moment, the first-gear transmission ratio of the rotor hub motor two-gear gearbox in the left rear wheel is (1+ k)₁)(1+k₂). Wherein k is₁For the characteristic parameter of the planet row of the first planetary gear train, k₁＞1，k₂And k2 is a characteristic parameter of the planet row of the second planetary gear train and is more than 1.

A forward two-gear state: no. 1 electromagnetic brakeWhen the device 210 is energized and the electromagnetic brake No. 2 225 is not energized, the first planetary gear train is in a free-wheeling state. The power output by the rotor hub motor 300 in the left rear wheel in the forward direction is transmitted to the left rear wheel 100 by the rotor output shaft 301 through the electromagnetic brake 1 210, the one-way clutch 211, the first planet row planet carrier 224, the second planet row sun gear 231 and the second planet row planet carrier 232 in sequence. At the moment, the second gear transmission ratio of the rotor hub motor two-gear gearbox in the left rear wheel is (1+ k)₂)。

A reverse gear state: electromagnetic brake No. 1 210 is not energized, and electromagnetic brake No. 2 225 is energized, at which time the first planetary gear set 223 is locked. The power reversely output by the rotor hub motor 300 in the rear left wheel is transmitted to the rear left wheel 100 through the rotor output shaft 301, the first planet row sun gear 221, the first planet row planet carrier 224, the second planet row sun gear 231 and the second planet row planet carrier 232 in sequence. At the moment, the reverse gear transmission ratio of the rotor hub motor two-gear gearbox in the left rear wheel is (1+ k)₁)(1+k₂)。

A neutral gear state: no. 1 electromagnetic brake 210 is not electrified, No. 2 electromagnetic brake 225 is not electrified, at the moment, the two electromagnetic brakes are simultaneously in an unlocked state, the gearbox is in a neutral gear state, and the power output by the rotor hub motor 300 in the left rear wheel cannot be transmitted to the left rear wheel 100.

As shown in fig. 3, the right rear wheel assembly applied to the embodiment of the hub motor two-gear transmission case of the present invention mainly comprises an inner rotor hub motor 400 and a double-row planetary gear type two-gear transmission case 500. The first planet row sun gear 521 of the two-speed gearbox 500 is in splined connection with the rotor output shaft 401 of the inner rotor hub motor 400, and the second planet row planet carrier 532 of the two-row planet gear type two-speed gearbox 500 is in splined connection with the rim of the right rear wheel 600.

The double-row planetary gear type two-gear transmission 500 mainly comprises a No. 1 electromagnetic brake 510, a one-way clutch 511, a first planet row sun gear 521, a first planet row planet gear 522, a first planet row gear ring 523, a first planet row planet carrier 524, a No. 2 electromagnetic brake 525, a second planet row sun gear 531, a second planet row planet carrier 532, a second planet row gear ring 533 and a second planet row planet gear 534. The four working states of forward first gear, forward second gear, reverse gear and neutral gear are mainly provided.

A forward first gear state: the electromagnetic brake No. 1 510 is not energized, and the electromagnetic brake No. 2 525 is energized, at which time the first planetary gear ring 523 is locked. The power output by the rotor hub motor 400 in the forward direction in the left rear wheel is transmitted to the left rear wheel 600 through the rotor output shaft 401, the first planet row sun gear 521, the first planet row planet carrier 524, the second planet row sun gear 531 and the second planet row planet carrier 532 in sequence. At the moment, the first-gear transmission ratio of the rotor hub motor two-gear gearbox in the left rear wheel is (1+ k)₁)(1+k₂) Wherein k1 is the characteristic parameter of the planet row of the first planetary gear train, k₁＞1，k₂Is a characteristic parameter, k, of the planet row of the second planetary gear train₂＞1。

A forward two-gear state: no. 1 electromagnetic brake 510 is electrified, No. 2 electromagnetic brake 525 is not electrified, and the first planetary gear train is in a free rotation state at the moment. The power output by the rotor hub motor 400 in the forward direction in the left rear wheel is transmitted to the left rear wheel 600 through the rotor output shaft 401, the electromagnetic brake 1, the one-way clutch 511, the first planet row planet carrier 524, the second planet row sun gear 531 and the second planet row planet carrier 532 in sequence. At the moment, the second gear transmission ratio of the rotor hub motor two-gear gearbox in the left rear wheel is (1+ k)₂)。

A reverse gear state: the electromagnetic brake No. 1 510 is not energized, and the electromagnetic brake No. 2 525 is energized, at which time the first planetary gear ring 523 is locked. The power reversely output by the rotor hub motor 400 in the left rear wheel is transmitted to the left rear wheel 600 through the rotor output shaft 401, the first planet row sun gear 521, the first planet row planet carrier 524, the second planet row sun gear 531 and the second planet row planet carrier 532 in sequence. At the moment, the reverse gear transmission ratio of the rotor hub motor two-gear gearbox in the left rear wheel is (1+ k)₁)(1+k₂)。

A neutral gear state: no. 1 electromagnetic brake 510 is not electrified, No. 2 electromagnetic brake 525 is not electrified, at the moment, the two electromagnetic brakes are simultaneously in an unlocked state, the gearbox is in a neutral gear state, and the power output by the rotor hub motor 400 in the left rear wheel cannot be transmitted to the left rear wheel 600.

As shown in fig. 4, the main control process of the synchronous gear shifting and speed changing method of the two-gear gearbox of the hub motor, which is applied to the distributed drive electric vehicle shown in fig. 1, is as follows:

step one, reading transmission ratio i of each gear of the transmission stored in a processor chip in real time by a VCU1100 of the vehicle control unit_kSteering wheel angle threshold δ_t(°), longitudinal gradient angle threshold α_t(rad), transverse slope angle threshold gamma_t(rad), Shift execution time threshold T_t(ms), brake pedal threshold BP_t(%), and the error threshold value epsilon of the rotating speed before gear shifting₁(r/min) and shift finish rotating speed error threshold epsilon₂(r/min), wheel radius R (m); the VCU1100 of the vehicle control unit obtains the current speed u of the vehicle and the gear state k of the two-gear transmission 200 of the current left wheel and the current rear wheel in real time through a sensor_l500-gear state k of right rear wheel two-gear gearbox_rSteering wheel rotation angle Delta (DEG), accelerator pedal opening AP (%), brake pedal opening BP (%), and 300 rotation speed n of left rear wheel hub motor_l(r/min) and 400 rotation speed n of hub motor of right rear wheel_r(r/min), longitudinal road slope α (rad), and transverse road slope γ (rad).

Step two, the VCU1100 of the vehicle control unit is used for controlling the vehicle according to the current steering wheel rotation angle delta (°), the longitudinal road gradient α (rad), the transverse road gradient gamma (rad) and the steering wheel rotation angle threshold delta (delta)_t(°), longitudinal gradient angle threshold α_t(rad), transverse slope angle threshold gamma_t(rad), judging whether the basic gear shifting condition is met. If delta is less than or equal to delta_t，α≤α_t，γ≤γ_tThe current vehicle and the road surface driving state are considered to be good, the basic gear shifting condition is met, otherwise, the current working condition is considered to be severe, and safe gear shifting is not facilitated.

And step three, the VCU1100 of the vehicle control unit judges the gear shifting working condition of the current vehicle according to the current accelerator pedal opening AP (%), and the current brake pedal opening BP (%). And if the AP is larger than 0, the BP is 0, the automobile is considered to be in an accelerating advancing state, and the automobile enters an upshift working condition, otherwise, the automobile is considered to be in a sliding or braking state, and the automobile enters a downshift working condition.

Gear shifting target vehicle speed u under gear-up working condition_tThrough the opening degree AP of the accelerator pedal and the target speed u of the gear shift_tDetermining the curve of (2); gear shifting target vehicle speed u under downshift working condition_tBy the brake pedal opening BP and the shift target vehicle speed u_tIs determined.

Step four, the vehicle control unit VCU1100 according to the gear shifting vehicle speed ut (Km/h) and the current transmission ratio i_kObtaining the gear-shifting target rotating speed n of the hub motor_t，

Wherein R is the vehicle tire radius.

Step five, the VCU1100 of the vehicle control unit shifts the target rotating speed n according to the motor_tAnd the current rotating speed n of the left and the rear wheel hub motors 300_lRotation speed n of hub motor 400 of right rear wheel_rAnd judging whether the current gear shifting condition is met or not. If | n_t-n_l|≤ε₁And | n_t-n_r|≤ε₁If the difference of the rotating speeds of the hub motors of the left and right rear wheels of the automobile is not large, the slip rates of the left and right rear wheels are within an allowable range, the gear shifting condition is met, the vehicle control unit VCU1100 sends a gear shifting instruction to the two-gear transmission controller TCU1200, otherwise, the vehicle control unit VCU1100 enters a gear shifting protection state, the original gear is maintained, the gear shifting is not carried out, and epsilon is₁Is a pre-shift speed error threshold.

And step six, after the two-gear transmission controller TCU1200 receives a gear shifting instruction of the vehicle control unit VCU1100, the two-gear transmission controller TCU controls the gear shifting executing mechanisms of the left rear wheel two-gear transmission 200 and the right rear wheel two-gear transmission 500 to perform gear shifting actions.

And step seven, the VCU1100 judges a gear shifting result according to the speed difference between the reference rotating speed and the actual rotating speed of the hub motor after gear shifting. Target threshold T at Shift time_tIn the vehicle, the VCU1100 passes the rotation speed n of the hub motor 300 of the current left rear wheel_lRotation speed n of hub motor 400 of right rear wheel_rAnd the new gear reference rotating speed n after gear shifting_tDifferential rotational speed of `And judging the gear shifting result. Wherein,

If T is less than or equal to T_t，|n_t’-n_l|≤ε₂，|n_t’-n_r|≤ε₂And if the requirements are met, the current two-gear gearbox of the hub motor of the left wheel and the right wheel is successfully shifted, and the VCU1100 of the vehicle control unit performs the reset operation of the shifting state. Otherwise, the gear shifting is failed, and the VCU1100 of the vehicle control unit sends a related instruction to perform gear shifting again according to the difference between the gear-up working condition and the gear-down working condition.

The synchronous gear shifting and speed changing method of the hub motor two-gear gearbox has certain difference on the control flow of the vehicle gear-up and gear-down working conditions, and is elaborated in detail by combining specific examples aiming at a distributed driving electric vehicle carrying a typical unpowered internal rotor hub motor two-gear gearbox.

1. Upshift condition

As shown in fig. 5, the control flow of the synchronous upshift and speed change of the two-gear gearbox of the hub motor according to the present invention is as follows:

step one, the VCU1100 of the vehicle control unit reads the transmission ratio i of each gear of the transmission stored in the processor chip in real time_kSteering wheel angle threshold δ_t(°), longitudinal gradient angle threshold α_t(rad), transverse slope angle threshold gamma_t(rad), Shift execution time threshold T_t(ms), brake pedal threshold BP_t(%), and the error threshold value epsilon of the rotating speed before gear shifting₁(r/min) and shift finish rotating speed error threshold epsilon₂(r/min), vehicle tire radius R (m); the VCU1100 of the vehicle control unit obtains the current speed u of the vehicle and the gear state k of the transmission 200 of the current left rear wheel in real time through a sensor_l500-gear state k of right rear wheel gearbox_rSteering wheel rotation angle Delta (DEG), accelerator pedal opening AP (%), brake pedal opening BP (%), and 300 rotation speed n of left rear wheel hub motor_l(r/min) and 400 rotation speed n of hub motor of right rear wheel_r(r/min), longitudinal road slope α (rad), and transverse road slope γ (rad).

Step two, the VCU1100 of the vehicle control unit is used for controlling the vehicle according to the current steering wheel rotation angle delta (°), the longitudinal road gradient α (rad), the transverse road gradient gamma (rad) and the steering wheel rotation angle threshold delta (delta)_t(°), longitudinal gradient angle threshold α_t(rad), transverse slope angle threshold gamma_t(rad), judging whether the basic gear shifting condition is met. If delta is less than or equal to delta_t，α≤α_t，γ≤γ_tThe current vehicle and the road surface driving state are considered to be good, the gear shifting condition is met, otherwise, the current working condition is considered to be severe, safe gear shifting is not facilitated, and the existing gears are maintained unchanged.

And step three, determining the upshift target vehicle speed. The VCU1100 of the vehicle control unit is used for controlling the vehicle speed u according to the opening degree AP of the accelerator pedal and the gear-up target vehicle speed u_tDetermining the upshift target vehicle speed u at the current accelerator pedal opening_t. Under the operating mode of upshifting, along with the increase of accelerator pedal aperture, the car needs to have stronger acceleration performance, and low-speed 1 keeps off and has the effect that the speed reduction increases and turns round, and acceleration performance is better, therefore the speed of a motor vehicle u of shifting gears when upshifting_tAs the accelerator pedal opening increases, there is an upward trend, which can be seen with reference to fig. 6. The specific gear-up target speed value needs to be determined by comprehensively considering the dynamic property and the comfort of the automobile in a real-vehicle calibration mode.

And step four, determining the target gear-up rotating speed of the hub motor. Target speed n for motor gear-up_t，

In the formula i₁Two-speed gearbox ratio u in 1 gear_tAnd (5) upshifting the target vehicle speed.

And fifthly, judging the gear shifting condition according to the speed difference between the target gear-up rotating speed and the actual rotating speed of the hub motor. The VCU1100 of the vehicle control unit shifts the target speed n according to the in-wheel motor_tAnd the current rotating speed n of the left and the rear wheel hub motors 300_lRotation speed n of hub motor 400 of right rear wheel_rAnd judging whether the current gear shifting condition is met or not.If | n_t-n_l|≤ε₁And | n_t-n_r|≤ε₁If the difference of the rotating speeds of the hub motors of the left and right rear wheels of the automobile is not large, the slip rates of the left and right rear wheels are within an allowable range, the gear shifting condition is met, the vehicle control unit VCU1100 sends a gear shifting instruction to the two-gear transmission controller TCU1200, otherwise, the vehicle control unit VCU1100 enters a gear shifting protection state, the original gear is maintained, the gear shifting is not carried out, and epsilon is₁Is a pre-shift speed error threshold.

And step six, the two-gear transmission controller TCU1200 controls the action of the gear shifting actuating mechanism. After the two-gear transmission controller TCU1200 receives the upshift instruction, it controls the electromagnetic brake No. 2 225 of the left and rear wheel two-gear transmission 200 to be powered off and the electromagnetic brake No. 1 210 to be powered on, and controls the electromagnetic brake No. 2 525 of the right and rear wheel two-gear transmission 500 to be powered off and the electromagnetic brake No. 1 to be powered on. The two-gear gearbox of the left and right rear wheels can simultaneously complete 1-gear up-shift and 2-gear up-shift actions.

And step seven, the VCU1100 of the vehicle control unit judges a gear shifting result according to the speed difference between the reference rotating speed and the actual rotating speed of the hub motor after the gear is shifted up. Reference rotating speed n of hub motor after gear-up_t’，

In the formula i₂For 2-gear two-gear transmission ratio, u_tThe actual speed after the gear-up and the state after the gear-shifting are mainly divided into the following two conditions:

(1) the shift was successful. If at the shift time threshold T_tInner, satisfy | n simultaneously_r-n_t’|≤ε₂，|n_l-n_t’|≤ε₂If the gear shifting is successful, the VCU1100 of the vehicle control unit resets the gear-up state, wherein n_rFor the rear right wheel hub motor to upshift rear rotation speed, n_lFor rear upshifting of the hub motor of the left rear wheel₂Is the shift end speed error threshold.

(2) The shift fails. When the gear shifting fails, the hub motor of one wheel is possibly in a neutral gear state, and the motor has larger torque output at the moment, so that the motor is easy to run away. The driving force output by the two wheels is different, so that a yaw moment is formed in the mass center of the automobile, and the automobile is easy to deviate from the driving direction. In the two cases, there are great potential safety hazards to the driver and the automobile, and the vehicle control unit VCU1100 performs the following operations:

step one, the vehicle control unit VCU1100 sends a zero-torque demand instruction to the left rear wheel hub motor controller MCU700 and the right rear wheel hub motor controller MCU900 at the same time, and the two motor controllers control the left rear wheel hub motor and the right rear wheel hub motor not to output torque.

And step two, the vehicle control unit VCU1100 sends a two-gear-returning and neutral-gear-engaging instruction to the two-gear transmission controller TCU1200, and the two-gear transmission controller TCU1200 controls the power failure of the electromagnetic brake No. 1 210 of the left and rear wheel two-gear transmission 200 and the power failure of the electromagnetic brake No. 1 510 of the right and rear wheel two-gear transmission 500 at the same time.

And step three, the vehicle control unit VCU1100 sends a gear shifting and two-gear increasing instruction to the two-gear transmission controller TCU1200 again, the two-gear transmission controller TCU1200 controls the electromagnetic brake No. 1 210 of the left rear wheel two-gear transmission 200 to be electrified simultaneously, and the electromagnetic brake No. 1 510 of the right rear wheel two-gear transmission 500 to be electrified.

And step four, the whole vehicle control VCU1100 sends a demand torque instruction to the left wheel motor controller and the right wheel motor controller, so that the left wheel motor and the right wheel motor recover power output.

And step five, judging the gear shifting result by the VCU1100 of the vehicle controller. If within the prescribed shift time threshold Tt, | n is simultaneously satisfied_t’-n_r|≤ε₂，|n_t’-n_l|≤ε₂If yes, the vehicle control unit VCU1100 resets the shift state.

Otherwise, the vehicle controller VCU1100 sends a shift 1 instruction to the two-gear transmission controller TCU1200, and the two-gear transmission controller TCU1200 controls the electromagnetic brake No. 2 225 of the left and rear wheel two-gear transmission 200 to be powered on, the electromagnetic brake No. 1 210 to be powered off, the electromagnetic brake No. 2 of the right and rear wheel two-gear transmission 500 to be powered on, and the electromagnetic brake No. 1 to be powered off to maintain the normal running function of the vehicle. And the VCU1100 of the vehicle control unit simultaneously sends a gear-up fault alarm signal to the instrument panel to remind a driver of cautious driving.

2. Downshift condition

As shown in fig. 7, the control flow of the synchronous downshift and shift of the two-gear gearbox of the hub motor according to the present invention is as follows:

step one, the VCU1100 of the vehicle control unit reads the transmission ratio i of the transmission gear stored in the processor chip in real time_kSteering wheel angle threshold δ_t(°), longitudinal gradient angle threshold α_t(rad), transverse slope angle threshold gamma_t(rad), Shift execution time threshold T_t(ms), brake pedal threshold BP_t(%), and the error threshold value epsilon of the rotating speed before gear shifting₁(r/min) and shift finish rotating speed error threshold epsilon₂(r/min), vehicle tire radius R (m); the VCU1100 of the vehicle control unit obtains the current speed u of the vehicle and the gear state k of the transmission 200 of the current left rear wheel in real time through a sensor_l500-gear state k of right rear wheel gearbox_rSteering wheel rotation angle Delta (DEG), accelerator pedal opening AP (%), brake pedal opening BP (%), and 300 rotation speed n of left rear wheel hub motor_l(r/min) and 400 rotation speed n of hub motor of right rear wheel_r(r/min), longitudinal road slope α (rad), and transverse road slope γ (rad).

And step three, judging the gear shifting condition according to the opening degree of the brake pedal. The VCU1100 of the vehicle control unit is used for controlling the vehicle according to the opening BP of the brake pedal and the limit threshold BP of the brake pedal_tComparing if BP is greater than or equal to BP_tThen the current steam is consideredThe vehicle is in an emergency braking state, the braking intensity is high, the braking time is short, safe gear shifting is not facilitated, the VCU1100 of the vehicle controller does not send a gear shifting instruction, and the existing gear is maintained. Otherwise, the current automobile state is considered to meet the gear shifting condition.

And step four, determining the target gear reduction speed of the hub motor. The VCU1100 of the vehicle control unit is used for controlling the vehicle speed u according to the opening BP of the brake pedal and the downshift target vehicle speed u_tDetermining a downshift target vehicle speed u at the current brake pedal opening_t. In the downshift condition, the driver may expect the vehicle speed to be lowered as quickly as possible as the opening degree of the brake pedal increases. Under the same wheel rotation speed, the first-gear low gear has the effects of reducing the speed and increasing the torque, and the time for decelerating the automobile can be reduced, so that the downshift target vehicle speed has a gradually increasing trend along with the increase of the opening degree of the brake pedal, which can be shown in fig. 8. The specific downshift target speed value is determined by taking the braking performance and comfort of the automobile into consideration and adopting a real automobile calibration mode.

And step five, determining the target rotating speed of the motor at the gear reduction point. Hub motor downshift target rotating speed n_t，

In the formula i₂Two-gear transmission ratio u when two gears_tAnd (5) downshifting the target vehicle speed.

And step six, judging the downshift condition according to the difference value between the rotating speed of the hub downshift target motor and the actual rotating speed. The VCU1100 of the vehicle control unit shifts the target speed n according to the electrical machinery_tAnd the current rotating speed n of the left and the rear wheel hub motors 300_lRotation speed n of hub motor 400 of right rear wheel_rAnd judging whether the current gear-down condition is met or not. If | n_t-n_l|≤ε₁And | n_t-n_r|≤ε₁If the difference of the rotating speeds of the hub motors of the left and right rear wheels of the automobile is not large, the slip rates of the left and right rear wheels are within an allowable range, the downshift condition is met, the VCU1100 of the vehicle controller sends a downshift instruction to the TCU1200 of the two-gear transmission case, otherwise, the VCU1100 of the vehicle controller enters a shift protection state, the original gear is maintained, and the gear shifting is not performed, wherein the VCU1100 of the vehicle controller is in the shift protection stateε₁A pre-shift speed error threshold.

And step seven, the two-gear transmission controller TCU1200 controls the action of the gear shifting executing mechanism. The two-gear transmission controller TCU1200 controls the electromagnetic brake No. 2 225 of the left rear wheel two-gear transmission 200 to be energized and the electromagnetic brake No. 1 210 to be de-energized simultaneously, and the electromagnetic brake No. 2 525 of the right rear wheel two-gear transmission 500 to be energized and the electromagnetic brake No. 1 510 to be de-energized simultaneously. The two-gear gearbox of the left and right rear wheels can simultaneously complete the actions of 2-gear reduction and 1-gear reduction.

And step eight, the VCU1100 of the vehicle control unit judges a gear shifting result according to the speed difference between the reference rotating speed and the actual rotating speed of the hub motor after gear shifting. Reference rotating speed n of hub motor after gear reduction_t’，

In the formula i₁Two-speed gearbox ratio u in 1 gear_tAfter the downshift, the actual vehicle speed and the shift result are mainly divided into the following two conditions.

(1) The shift was successful. If at the shift time threshold T_tInner, satisfy | n simultaneously_r-n_t’|≤ε₂，|n_l-n_t’|≤ε₂If the downshift is successful, the VCU1100 of the vehicle controller resets the downshift state, wherein n_rFor the rear right wheel hub motor to downshift the rear rotational speed, n_lFor the rear-wheel hub motor downshifting rear speed, epsilon₂Is the shift end speed error threshold.

(2) The shift fails. When a downshift is normally performed, the accelerator pedal opening is zero, and the motor torque is zero, at this time, the vehicle control unit VCU1100 performs the following operations:

step one, the vehicle control unit VCU1100 sends a 1 gear-reversing neutral gear-engaging instruction to the two-gear transmission controller TCU 1200. The two-gear transmission TCU1200 simultaneously controls the electromagnetic brake No. 2 225 of the left rear wheel two-gear transmission 200 to be de-energized, and the electromagnetic brake No. 2 525 of the right rear wheel two-gear transmission 500 to be de-energized.

And step two, the vehicle control unit VCU1100 sends a gear 1 engaging command to the two-gear transmission controller TCU 1200. The two-gear transmission TCU1200 controls the electromagnetic brake No. 2 225 of the left rear wheel two-gear transmission 200 to be energized and the electromagnetic brake No. 2 525 of the right rear wheel two-gear transmission 500 to be energized at the same time.

And step three, the VCU1100 of the vehicle control unit judges the gear shifting result. If at the prescribed shift time threshold T_tInner, satisfy | n simultaneously_t’-n_r|≤ε₂，|n_t’-n_l|≤ε₂The downshift is deemed successful. The vehicle control unit VCU1100 performs a shift state reset.

Otherwise, the downshift is failed again, and in order to maintain the normal running function of the automobile, the vehicle control unit VCU1100 sends a command of restoring the original gear 2 to the two-gear transmission controller TCU 1200. The two-gear transmission controller TCU1200 simultaneously controls the electromagnetic brake No. 2 225 of the left rear wheel two-gear transmission 200 to be powered off and the electromagnetic brake No. 1 210 to be powered on, and controls the electromagnetic brake No. 2 525 of the right rear wheel two-gear transmission 500 to be powered off and the electromagnetic brake No. 1 510 to be powered on. And the VCU1100 of the vehicle control unit simultaneously sends a gear-down fault alarm signal to the instrument panel to remind a driver of cautious driving.

While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.

Claims

1. A synchronous gear shifting and speed changing method for a two-gear gearbox of an in-wheel motor is characterized by comprising the following steps:

step one, reading transmission ratio i of each gear of a gearbox stored in a processor chip in real time by a VCU of a vehicle control unit_kSteering wheel angle threshold δ_tLongitudinal slope angle threshold α_tTransverse slope angle threshold gamma_tShift execution time threshold T_tBrake pedal opening degree threshold BP_tBefore-shift speed error threshold epsilon₁Speed error threshold epsilon after gear shifting₂A wheel radius R;the VCU of the vehicle controller acquires the current speed u of the vehicle, the gear state k of a left gearbox and a right gearbox, the steering wheel angle delta, the accelerator pedal opening AP, the brake pedal opening BP and the rotating speed n of a hub motor of a left wheel in real time through a sensor_lRight wheel hub motor speed n_rA longitudinal road slope α and a transverse road slope γ;

2. The in-wheel motor two-gear gearbox synchronous shifting and speed changing method according to claim 1, wherein in the second step, the VCU of the vehicle control unit judges basic conditions of shifting according to the current automobile state and road surface working conditions as follows:

if delta is less than or equal to delta_t，α≤α_t，γ≤γ_tThe current vehicle and road running state is considered to be good, the gear shifting condition is met, otherwise, the current working condition is considered to be poor, the safe gear shifting is not facilitated, the vehicle control unit VCU enters a gear shifting protection state, the gear shifting instruction is not sent, and the gearbox maintains the existing gear;

3. The in-wheel motor two-gear gearbox synchronous shifting method according to claim 1, wherein in the third step, the condition that the vehicle control unit VCU judges the vehicle shifting condition is as follows:

if AP is greater than 0 and BP is 0, the automobile is considered to be in an accelerated advancing state, the driver has the intention of increasing the speed of the automobile and enters a gear-up working condition, otherwise, the automobile is considered to be in a sliding or braking state, the driver has the intention of reducing the speed of the automobile and enters a gear-down working condition;

4. The in-wheel motor two-gear gearbox synchronous shifting method according to claim 1, wherein in the third step, the determination method of the target shifting speed is divided into the following two types according to different driving conditions of the automobile:

(1) under the working condition of gear-up, determining according to the curve of the opening of an accelerator pedal and the target speed of the gear-up;

with the increase of the opening degree of an accelerator pedal, the automobile needs to have strong acceleration performance, the low-speed gear 1 has the functions of reducing and increasing torque, and the acceleration performance is good, so that the target speed u of the automobile during gear-up_tThe method has the advantages that the method has an ascending trend along with the increase of the opening degree of an accelerator pedal, and the specific gear shifting target speed value needs to be determined in a real vehicle calibration mode by comprehensively considering the dynamic property and the comfort of the vehicle;

(2) under the downshift working condition, determining according to a curve of the opening of a brake pedal and a downshift target vehicle speed;

with the increase of the opening BP of the brake pedal, a driver has the intention of quickly decelerating the automobile, and if the downshift target speed is increased, the automobile can enter a low-speed gear as soon as possible to realize quick deceleration; thus the shift target vehicle speed u at downshift_tThe method has the advantages that the method has an ascending trend along with the increase of the opening degree of a brake pedal, and the specific gear shifting target speed value needs to be determined in a real vehicle calibration mode by comprehensively considering the braking performance and the whole vehicle comfort;

5. The in-wheel motor two-speed gearbox synchronous shifting method according to claim 1, wherein in step four, the in-wheel motor shifting target speed n_tComprises the following steps:

6. The synchronous shifting and speed changing method for the two-gear gearbox of the hub motor according to claim 1, wherein in the step five, the conditions for the VCU to perform shifting judgment according to the speed difference between the target speed and the actual speed of the hub motor of the left and right wheels are as follows:

if | n_t-n_l|≤ε₁，|n_t-n_r|≤ε₁If the difference of the rotating speeds of hub motors of the left wheel and the right wheel of the automobile is not large, the slip rates of the left wheel and the right wheel are within an allowable range, the gear shifting condition is met, and the VCU of the whole automobile controller sends a gear shifting instruction to the TCU of the transmission case controller; otherwise, the current driving state of the automobile is not favorable for safe gear shifting, the VCU of the vehicle controller enters a gear shifting protection state, no gear shifting instruction is sent, and the gearbox maintains the existing gear;

wherein n is_tFor shifting target speed, n, of the in-wheel motor_lIs the actual rotating speed of the hub motor of the left wheel, n_rIs the actual rotating speed of the hub motor of the right wheel₁For shifting front speedAn error threshold.

7. The synchronous shifting and speed changing method for the two-gear gearbox of the hub motor according to claim 1, wherein in the seventh step, the VCU of the vehicle control unit determines the shifting result according to the speed difference between the reference rotating speed and the actual rotating speed of the hub motor after the left and right wheels are shifted, and the conditions of the shifting result are as follows:

if T is less than or equal to T_t，|n_t’-n_l|≤ε₂，|n_t’-n_r|≤ε₂If the conditions are met, the current two-gear gearbox of the hub motors of the left wheel and the right wheel is successfully shifted, and the VCU of the vehicle control unit performs a shifting state resetting operation; otherwise, if the gear shifting fails, the VCU sends a related instruction to perform gear shifting again according to the difference between the gear-up working condition and the gear-down working condition;

8. The synchronous gear shifting and speed changing method for the two-gear gearbox of the in-wheel motor according to claim 7, wherein the new-gear in-wheel motor reference rotating speed n_t' is:

9. The in-wheel motor two-gear gearbox synchronous gear shifting speed changing method according to claim 7, wherein the step of performing gear shifting again when the automobile fails to shift under the gear-up working condition is as follows:

step one, a VCU of a vehicle control unit sends a torque clearing instruction to a hub motor controller to enable the output torque of hub motors of left and right wheels to be zero;

step two, the VCU of the vehicle control unit sends a two-gear exit instruction to the TCU of the gearbox controller, so that the two-gear gearbox of the left wheel and the right wheel is in a neutral gear state;

step three, the VCU sends a two-gear-hanging instruction to the TCU, and the TCU controls the gear-shifting actuating mechanism of the two-gear gearbox of the left wheel and the right wheel to act;

step four, the VCU of the vehicle control unit sends a torque demand instruction to the hub motor controller again to enable the hub motors of the left wheel and the right wheel to recover torque output again;

if T is less than or equal to T_t，|n_t’-n_l|≤ε₂，|n_t’-n_r|≤ε₂If the conditions are met, the current two-gear gearbox of the hub motors of the left wheel and the right wheel is successfully shifted, and the VCU of the vehicle control unit performs a shifting state resetting operation; otherwise, if the two-gear gearbox fails to upshift for two times continuously, the gearbox can be considered to have an upshift fault, the gearbox recovers the first gear state again in order to maintain the power output of the automobile, and the vehicle control unit VCU sends an upshift failure alarm to the instrument panel to prompt a driver to drive cautiously and reasonably according to the current fault information of the automobile;

10. The in-wheel motor two-gear gearbox synchronous gear shifting speed changing method according to claim 7, wherein the step of performing gear shifting again when the automobile fails to shift under the gear-shifting working condition is as follows:

step one, a VCU of a vehicle control unit sends a first gear quitting instruction to a TCU of a gearbox controller, so that a left and right wheel two-gear gearbox is in a neutral gear state;

step two, the VCU sends a first gear engaging command to the TCU, and the TCU controls the gear shifting actuating mechanism of the left and right wheel two-gear gearbox to act;

if T is less than or equal to T_t，|n_t’-n_l|≤ε₂，|n_t’-n_r|≤ε₂If the conditions are met, the current two-gear gearbox of the hub motors of the left wheel and the right wheel is successfully shifted, and the VCU of the vehicle control unit performs a shifting state resetting operation; otherwise, if the two-gear gearbox fails to downshift continuously for two times, the gearbox can be considered to have a downshift fault, in order to maintain the normal running function of the automobile, the gearbox restores the two-gear state again, and the vehicle control unit VCU sends a downshift failure alarm to the instrument panel to prompt a driver to drive cautiously and reasonably according to the current fault information of the automobile;